Astronomers are observing the universe across many different regions of the electromagnetic spectrum, from gamma rays to radio waves. a. True
b. False

before we can answer, we have to see the choices that are printed there with the question.   that's the only way we can point you to the correct one.

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.

a sonic boom is a loud boom that breaks the sound barrier

explanation: