The diameter of a gold nucleus is about 10^-15 m. Because gold is fairly massive, this implies a very high nuclear density. What's the density of a gold nucleus, in kilograms per cubic meter? The mass of a gold atom is a good approximation for this purpose.

mass and volume are the answers you are looking for

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.