The secondary structure of a protein results from

multiple allele inheritance is traits controlled by more than 2 alleles (ex: pigeons having 3 alleles of one gene govern their feather color).   so the answer is a.

d. planting trees

the trees take in carbon to make oxygen.

plato users:

d.  

there was a variety of food available on island x, but there were only large seeds and nuts on island y.