Wrong answers:
A and B both state that solids are fluid while gases are not, while in reality, it is the opposite. Gases are fluid while solids are not.
C states the inverse of D, so C is incorrect.
Correct answer:
D. Solids have low energy levels and gases have high energy levels
This is because matter is in gas form when the temperature is higher and when the matter has absorbed more heat. More heat means more energy, so gases contain more energy than solids.
Matter, or "stuff", can be in multiple states, such as solid and gas.
The state of matter depends on how much energy the matter has absorbed.
Matter becomes a gas as more energy is added, and becomes a solid as more energy is removed.
This makes sense, because the individual molecules in a solid don't move as much, while the molecules in a gas move around quite a lot.
This makes gases easier to move around and change shape than solids.
Generally, as matter absorbs more heat and turns from solid to liquid to gas, the matter expands, and takes up more space.
This is because the more energy matter has, the more the molecules move and vibrate around, meaning they need more space to do so, so they expand.