Two types of transport of molecules across a cell membrane are: Transport 1: Solute molecules move across the cell membrane along their concentration gradient; requires no energy expenditure. Transport 2: Solute molecules move across the cell membrane against their concentration gradient; requires expenditure of energy. Which statement is CORRECT? A) Transport 1 describes passive transport by diffusion. B) Transport 2 describes passive transport by the Na+/K+ pump. C) Transport 2 describes passive transport by a carrier protein. D) Transport 1 describes facilitated transport of substances through the membrane.