Question

semipermeable means...
only water can get through.
everything can get through.
nothing can get through.
only some things can get through.

Explanation:

A semipermeable membrane allows only certain substances (usually small molecules like water, but not limited to water) to pass through while blocking others. It is not completely permeable (so not everything can pass through) and not impermeable (so not nothing can pass through).

Answer:

only some things can get through.