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The correct option is the water level will not change.

CONCEPT:

• The density of ice is less than that of water that's why it floats on the water,

Mass (M) = ρ × V

• Consider two cases, in the first case an ice cube of mass m floating in the water, if it is floating (in equilibrium), it will have to displace enough water to support its weight.
• In the second case, where the ice has melted, it turns into the water of volume,  exactly the same volume as it displaced before.

EXPLANATION:

If a piece or cube of ice is placed in a container containing water, some of its portions will remain out of the water level. As we know the fact that the volume of ice is greater than that of the water so after melting the volume of the piece will decrease and the water level will remain the same.

The correct answer is Galvanometer - Electric resistance.

EXPLANATION:

Additional Information

The correct option is all the three will reach the ground together.

CONCEPT:

• A fall is considered a free fall if the only force acting on it was gravity.
• As the vacuum contains no matter, there is no opposite force against the free fall due to gravity.
• In air and atmosphere, there is aerodynamic drag and in the sea, there is a buoyancy force of water to oppose the movement due to gravity.

EXPLANATION:

• The time required to hit the ground for all the three balls depends on only gravitational acceleration (g) which is the same for all the three balls because there is no air resistance present in a vacuum.
• It is the condition of free fall so, If a feather, a rubber ball, and a wooden ball are falling freely simultaneously from the same height in a vacuum, then all the three will reach the ground together

The correct answer is an interference of light.

CONCEPT:

• When light shines onto a bubble it seems to change colour.
• Not like those seen during a rainbow, which arises from differential refraction, the colours are seen during a soap bubble that arises from interference of light reflecting off the front and back surfaces of the thin film.
• Interference is a natural phenomenon that happens at every place and at every moment.
• Interference is the phenomenon in which two waves superpose to form the resultant wave of the lower, higher, or same amplitude.
• The most commonly seen interference is an optical interference or light interference.
• This is because light waves are randomly generated every which way by most sources.
• This means that light waves coming out of a source do not have a constant amplitude, frequency, or phase.
• The most common example of interference of light is the soap bubble which reflects wide colours when illuminated by a light source.

Additional Information

• Scattering, in physics, is a change in the direction of motion of a particle because of a collision with another particle.
• In optics, dispersion is the phenomenon in which the phase velocity of a wave depends on its frequency.
• Polarization is a property applying to transverse waves that specify the geometrical orientation of the oscillations.

The correct option is the sum of the numbers of neutrons and protons.

CONCEPT:

• ATOMIC NUMBER: It is defined as the number of protons present in the nucleus. It is denoted by the letter Z.

• MASS NUMBER: The total number of protons and neutrons present in a nucleus is called the mass number of the element. It is denoted by the letter A.

• For neutral atom,

1. Number of protons in an atom = Z
2. Number of electrons in an atom = Z
3. Number of nucleons in an atom = A
4. Number of neutrons in an atom = N = A – Z

EXPLANATION:

From the above, it is clear that the mass number of a nucleus is the sum of the numbers of neutrons and protons

The correct option is Limestone.

EXPLANATION:

• A limestone is a form of calcium carbonate which is used extensively for the manufacture of cement.
• Cement is manufactured through a closely controlled chemical combination of calcium, silicon, aluminum, iron, and other ingredients.
• Crushed limestone is often the main raw ingredient in the manufacture of portland cement.
• CaCO3 is the chemical formula of Calcium carbonate.
• Limestone is a carbonate sedimentary rock composed primarily of calcium carbonate (CaCO3).
• Limestone released carbon dioxide gas while heating.

The correct option is the mass number.

EXPLANATION:

• Isotopes are atoms of the same element that have different numbers of neutrons but the same number of protons and electrons.
• The difference in the number of neutrons between the various isotopes of an element means that the various isotopes have different masses.

So, The difference in isotopes of an element is the mass number.

Additional Information

Isotopes: It is defined as the atoms which have the same number of protons (or same atomic number) but have different neutrons.

Isomers: The two or more compounds having the same formula but a different arrangement of atoms in the molecule and different properties are called isomers.

Isotones: The nuclei having an equal number of neutrons (A-Z) but different numbers of protons (Z) and different mass numbers (A) are called isotones.

Isobars: The nuclei which have the same mass number (A) but a different atomic number (Z) are called isobars.

The correct option is triple point.

CONCEPT:

• The temperature and pressure at which the solid, liquid, and vapor phases of a pure substance coexists in equilibrium are called the triple point.​
• The Triple point is a line on the P-V diagram where all the three phases solid, liquid, and gases exist in equilibrium.
• The triple point is merely the point of intersection of the sublimation and vaporization curves.
• It has been found that on a ‘p-T’ diagram the triple point is represented by a point and on a ‘p-v’ diagram it is a line, and on a ‘u-v’ diagram it is a triangle.
• In the case of ordinary water, the triple point is at a pressure of 4.58 mm Hg and a temperature of 0.01°C.
• The matter solidifies on the left side of the triple point, not at the triple point.
• The matter liquifies on the upper side of the triple point, not at the triple point.
• The matter sublimates on the right side of the triple point, not at the triple point.

The correct option is bauxite.

EXPLANATION:

• Ore is a naturally occurring mineral or rock from which metal can be extracted.
• Aluminum (Al) is a chemical element lightweight silvery-white metal of main Group 13 of the periodic table.
• Aluminum is the most abundant metallic element in Earth’s crust and the most widely used nonferrous metal.
• Because of its chemical activity, aluminum never occurs in the metallic form in nature, but its compounds are present to a greater or lesser extent in almost all rocks, vegetation, and animals.
• Aluminum is concentrated in the outer 16 km (10 miles) of Earth’s crust, of which it constitutes about 8 percent by weight, it is exceeded in amount only by oxygen and silicon.
• Bauxite ore is the main source of aluminum and contains the aluminum minerals gibbsite, boehmite, and diaspore.
• Aluminum is used in the United States in packaging, transportation, and building.
• Because it is a mixture of minerals, bauxite itself is a rock, not a mineral.

Additional Information​ 

• Calamine is an ore of Zinc (Zn) with the chemical formula Fe2O4Zn.
• Calcite is a rock-forming mineral with a chemical formula of CaCO3.
• Galena is an ore of Lead (Pb) with the chemical formula PbS. It is also called Lead Glance.

The correct option is the  Basic solution.

CONCEPT:

• The pH of the pH scale stands for the power of Hydrogen. It consists of the value from 0 to 14.
• The pH scale in Chemistry is used to determine the acidity or basicity of a solution.
• The pH scale indicates the concentration of Hydrogen ions in the solution.
• Litmus, turmeric, red cabbage, China rose, etc. are some common natural indicators used widely to show the acidic or basic character of substances.
• Litmus is obtained from lichens. The solution of litmus is purple in color.
• Litmus paper comes in two colors – blue and red. An acid turns blue litmus paper into red. A base turns red litmus paper into blue.
• The pH value of an acidic solution is less than 7.
• The pH value of a Basic solution is more than 7.​

Additional Information