The period of a mechanical wave is 12 seconds. what is the frequency of the wave?

12 waves/second
4.0 waves/second
0.083 waves/second
depends on the speed of the wave

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.

the duration of a photographic flash is related to an rc time constant, which is 0.100 μs for a certain camera.