4. there are two categories of ultraviolet light. ultraviolet a (uva) has a wavelength ranging from 320 nm to 400 nm. it is not harmful to the skin and is necessary for the production of vitamin d. uvb, with a wavelength of 280 nm and 320 nm, is much more dangerous because it causes skin cancer. what are the frequency ranges for uva and uvb light?

the earths atmosphere is made up of nitrogen and oxygen. solids can turn into gasses through a process called sublimation. sublimation is the transition of a substance directly from the solid to the gas phase, without passing through the intermediate liquid phase.

hope this : d

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.

where’s the list ? the question is incomplete

that would be because of both gravity and friction. so     c