B is true because liquids are still more compact than gases, although they are loose, they aren't completely free. They also don't have a definite volume, making them assume the shape of their container. As for compression, liquids are harder to compress compared to gases.
Answer: A balanced equation for the given reaction is
.
Explanation:
The reaction equation will be as follows.

Number of atoms on the reactant side is as follows.
Number of atoms on the product side is as follows.
Since number of atoms on both the reactant and product sides are equal. Hence, the reaction equation is balanced.
Thus, we can conclude that a balanced equation for the given reaction is
.
I think the answer is D. the upper surface of undergound water.
Answer : The correct option is, pressure.
Explanation :
The ideal gas equation is,

where,
P = pressure of the gas
V = volume of the gas
n = number of moles of gas
T = temperature of the gas
R = gas constant
The value of 'R' has several different values which are :




That means, the value of 'R' is different due the change in the pressure value and all the variables (temperature, volume and moles) are constant.
Hence, the correct option is, pressure.