One Y and one X chromosome.
An action potential involves the transfer SODIUM and POTASSIUM ions across an axon's membrane.
During depolarization, when the ion channels open, they allow the influx of sodium ions into the cell, thus changing the electro-chemical gradient of the cell, in order to counter balance this, potassium ions will be allowed to flow out of the cell.<span />
C.
Biotic mean alive, so we can cut off the first 2 easily. Aquatic birds eat frogs, so that one is safe for now. A decrease in something parasitic usually helps the population, so D is out too. The only one left is C.