"Research suggests that Mars has some features that would support life, but most conditions are too harsh for it." is <span>definitely</span> a main idea as for the second one your best bet is to talk about possible life on mars in the future so that 4th sentence is going to be your friend.
The prepositional phrase in the sentence is best friend
The word aesthetic is most closely related to beauty.
<span>Various normal eye activities, such as depth perception, eye aiming and alignment, oculomotility, convergence and divergence, and accommodative ability.</span>
Answer:
C I think I'm so so sorry if I get it wrong