Since the particles of gas all try to separate and move into equilibrium when exposed to space, all of the particles have been moved out to a certain ratio of particle per air, if that makes sense. When moved to a bigger space, the concentration of the particles aren't as condensed. So therefore, the particles will move out and put more space in between each particle. They will all be spaced out, and there will be less total particles of gas per square inch of air.
1) The first reactant is incomplete.
2) The reaction is a combustion reaction and it is easy to infere that it is the combustion of the alkane with 3 carbons.
3) The general chemical formula of the alkanes is

4) Hence the equation is:

5) The name of the alkane is propane, so the word equation is:
propane + oxygen → carbon dioxide + water
6) The equation is unbalanced. This is the balanced equation:

7) It is, as the combustion of any hydrocarbon, a redox (reduction-oxidation) reaction, where the carbon is oxidized and the oxygen is reduced.
8) This kind of reactions release a lot of energy.
A describes a gymnosperm.
B describes any type of plant.
C is too vague to even describe a plant.
D (the correct answer) describes an angiosperm (flowering plant). After double fertilization, angiosperms form a fruit over the ovulary of the plant, where the seeds are located.