The acceleration of an object is the slope of its velocity-time graph.
True
False

the entire statement is true and correct.  

there's no diagram, nothing is illustrated, and no question is asked.

a.) travels faster in solids because the particles are closer together.

air is a gas water is a liquid

answer;

d. are made mostly of liquid

explanation;

-the general   composition and structure planets includes; they have a thick gas and liquid layer covering a small,solid core. mostly the gases are hydrogen and helium atmosphere and layers of liquid hydrogen. for instance neptune and uranus are examples of the outer planets, they have a core covered by ice and ammonia.

-neptune's atmosphere is hydrogen and helium with a bit of methane so there is no oxygen to breath and the interior is made up of frozen water and ammonia with a rock and iron core. thus, there is no liquid water or solid surface to survive.