Here's why:

* Osmosis is the movement of water molecules across a selectively permeable membrane from an area of high water concentration to an area of low water concentration.

Let's look at the other options:

* A process by which the cytoplasm divides: This describes cytokinesis, which is part of cell division.

* DNA synthesizes: This describes DNA replication, the process of copying DNA.

* molecules distribute balanced movement: This is a vague description that doesn't accurately represent osmosis.

Therefore, the most accurate and specific description of osmosis is that it is the movement of water across a selectively permeable membrane.