Which nitrogen base sequence is the partner of T-C-A-G-C-A? A-C-G-A-CIES
C-A-G-A-T-G
A-G-T-C-G-T
O T-C-A-G-C-A

Which of the following is a reason why early living organisms on earth could not have survived on the surface? 1. the lack of an ozone layer 2. the lack of oxygen in the atmosphere 3. the fact that these organisms were single-celled