Answer:
A.the flow of energy between organisms in an ecosystem
The alveoli. These little air sacs are found on the end of the bronchioles and are the place where oxygen enters the blood and the carbon dioxide leaves.
Adenine to thymine and cytosine to guanine are the base pairings during DNA replication.
Viruses reproduce by inserting their genetic code into the genetic code of a cell, from there, an active virus will copy itself over and over until that cell bursts, where the new viruses can repeat the process. Another type of virus inserts itself into the genetic code, but does not actively reproduce. It sits and waits for the cell to reproduce for it, by splitting in the way cells do.
