A scientist is modeling the movement of water through the atmosphere. Which is an input into this system? Choose the correct answer.?
An input is something that puts into a system (in this case water). So of the 4 choices you list, which ones put water into the atmosphere...? A and D are water coming OUT of the atmosphere. So you now can figure out which are putting water INTO the atmosphere.
Do your own homework.
Which of the four choices *adds* water to the atmosphere? 'A' doesn't--it removes water. Vapor rising or condensing don't either. So that only leaves you with one choice, right? . .