A

al s3x the riskiest s3xual activity for HIV transmission. (Haha sorry for the pi and 3s it won't let me submit some of those words)
Amino acids. Every protein is a long chain of amino acids.
Living things:-
-Living things are made of cells.
-Living things have and use energy.
-Living things grow and develop.
-Living things reproduce.
-Living things respond to their environment.
-Living things adapt to their environment.
That answer is A. Hopefully this helps.