Unit 4 review grade 5

I’m doing some practice exam questions for biology, and i’m not sure how to do these 3 parts to the question.

What best explains the inability for life to exist in earth early atmosphere

If t=tall and t=short what will be the physical appearance of the offspring the cross below? a.some will be tall and some will be short b.they will all be tall c.they will all be short d.they will be medium height