Answer:
I believe the answer is C. Location 3
I might be wrong though, sorry if I am.
They would know if they see anything like traces of water or anything else that would be nessecary for a living organism to have. They look for these with technology like the hubble telescope as well as the drone on Mars to gather as much information as possible.
I think the answer is ozone i hope i am right and hope this helps
I believe the answers are A. C. D.
