Complementary DNA (cDNA) is a DNA copy of a messenger RNA (mRNA) molecule produced by reverse transcriptase, a DNA polymerase that can use either DNA or RNA as a template.
Answer:
humans killing whales caused orcas to have to eat otters which caused sea urchin populations to increase which caused kelp populations to decrease
Explanation:
The answer is A because the males sperm determines the sex of a baby.The determines sperm is carrying an X or Y chromosome.