Answer: The correct answer for the blank is-
facilitated diffusion and
active transport.
Facilitated diffusion is a type of passive transport (transport of solute from high area of concentration to lower area of concentration) that requires transport protein ( which work as transporters or channels for the transport of solute).
Active transport also requires transport proteins/ carrier proteins (which work as pump) to drive the transport of solutes against the concentration gradient. This process utilizes energy (obtained from hydrolysis of ATP) for the transport because solute move from high concentration to an area where their concentration is less.
B) low concentration of dissolved oxygen, and farming in the Midwest
C) high concentration of nitric oxides and burning coal to generate electricity in the Northeast.
D) low concentration of dissolved phosphates an Barge traffic on the Mississippi River