Which of these is the best definition for osmosis?

Question

1. The diffusion of water water through a partially permeable membrane from a dilute solution to a concentrated solution up a concentration gradient
2. The net movement of particle from an area of low concentration to a high concentration.
3. The diffusion of a gas through a partially permeable membrane from a dilute solution to a concentrated solution down a concentration gradient
4. The diffusion of water water through a partially permeable membrane from a dilute solution to a concentrated solution down a concentration gradient.

Answer 1

The best definition for osmosis is option 1: The diffusion of water through a partially permeable membrane from a dilute solution to a concentrated solution up a concentration gradient.