Final answer:
Passive transport requires a concentration gradient to allow substances to move from an area of higher concentration to one of lower concentration without the use of energy. It's not limited to water and does not involve the cell wall or endocytosis. The option (A) is correct.
Step-by-step explanation:
Among the options provided regarding passive transport, the true one is that it requires a concentration gradient. Passive transport is the movement of substances across a cell membrane without the need for energy input, occurring down the concentration gradient, from an area of higher concentration to an area of lower concentration. This includes processes such as passive diffusion and facilitated diffusion.
Passive transport does not involve the cell wall, which is not present in all cells but is in plant cells, nor does it include endocytosis, which is an active transport process requiring energy. Also, passive transport is not limited to only moving water; it allows various substances like gases, water (through aquaporins), and other molecules needing no energy for their translocation to pass through the cell membrane. Therefore, option (A) is correct.
This question is not complete, Here I am attaching the complete question:
Which of the following is true of passive transport?
(A) it requires a concentration gradient
(B) it uses the cell wall
(C) it includes endocytosis
(D) it only moves water