Explanation:

Let’s break it down:

- Animals use specialized proteins called actin and myosin for movement. These are the muscle fibers that actually contract and create motion.

- Plants, on the other hand, don’t have these muscle proteins. Their movements, like opening and closing stomata or the folding of leaves in touch-me-not, mostly happen because water moves in or out of their cells. This is called turgor movement.

- Option 1 (nature of plasma membrane): While the plasma membrane is important, it isn’t the main driver for movement in plants.

- Option 3 (amount of enzyme): Enzymes help with chemical reactions, but play little direct role in plant movement.

- Option 4 (none of these): Not correct—there is a right answer here.

So your answer, Option 2: amount of water is spot on. The real reason plants move is due to water changes inside their cells.