C. Both A. and B.
Explanation:
Statement A. Reducing the volume is true because of Boyle's law, which states that for a gas at fixed temperature, the pressure p and the volume V are inversely proportional:

Therefore, when the volume V is reduced, the pressure p increases.
Statement B. Adding more gas is also true: in fact, if we add gas into the container, we will have more molecules of the gas hitting the wall of the container. But the pressure of a gas is exactly given by this: by the collision of the molecules against the wall of the container, so the more the molecules of gas, the greater the pressure.
Answer:
In water, the particles are much closer together, and they can quickly transmit vibration energy from one particle to the next.
A water wave is an example of a transverse wave. As water particles move up and down, the water wave itself appears to move to the right or left.
Answer:
Explanation:
Given
Each student exert a force of 
Let mass of car be m
there are 18 students who lifts the car
Total force by 18 students 
therefore weight of car 
mass of car 

(b)
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Answer:
Nuclear energy is that released by dividing the nuclei of heavy atoms (also called under the name Nuclear Fission)
Explanation:
In this process, a large amount of heat is generated that can be used to obtain mechanical energy, which is used to generate electrical energy.
Nuclear energy is a sustainable source of energy having a low impact on the environment.