Identify the structure in blood that transports oxygen to body cells.

Red blood cells

Hemogoblin

Explanation:

"The protein inside (a) red blood cells that carries oxygen to cells and carbon dioxide to the lungs is (b) hemoglobin. Hemoglobin is made up of four symmetrical subunits and four heme groups. Iron associated with the heme binds oxygen."

well, that's easy; the answer's c, "it reduces contamination of the water and substrate of the estuary."

i believe it would be c: tons.