Answer:
D. Active transport.
Explanation:
Active transport is the method that uses the ATP's energy to move ions and molecules from one side to the other of the membrane. The elements move from a place of lower concentration to one of a higher concentration. They move against their concentration gradient, which is why they need the energy to do it. There are two types of active transport, primary and secondary.
The primary active transport is ion pumps that hydrolyze ATP using one of the phosphates of the ATP to change the pump's shape and move the elements against their concentration gradient. It uses the ATP's energy directly.
The secondary active transport does not use ATP directly. It uses the electrochemical gradient that the primary transport had created when hydrolyzing ATP to transport the ions and molecules.
Only 200 out of 2 000, 000 sperm cells reach the ovum. And only one (in exception to very rare cases of two) sperm cells actually participate in the process of fertilization. In comparison, an average female only produces 400 of egg cells during their lifetime, but the eggs cells are significantly larger than sperm cells.
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