Two loud speakers are located 4.00 m apart and are playing an in phase tone of 97.0 hz which under conditions of a nominal speed of sound of 340.0 m/s has a wavelength of
3.51 m.
How far from the left speaker would you need to stand to hear the tones from the
two speakers cancel out so that you would hear nothing?

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.