Question

what does it mean for a membrane to be selectively permeable?
only certain molecules are allowed to pass through.
the membrane is rigid and only allows water to pass through.
all types of molecules are able to pass into the cell.
the membrane is rigid and nothing can enter or leave the cell.

Explanation:

A selectively permeable membrane regulates molecular passage by permitting only specific substances (based on factors like size, charge, or solubility) to cross, while blocking others. The incorrect options are wrong because: the membrane is not rigid (it's typically flexible), it does not only allow water through, it does not let all molecules pass, and it does not block all movement.

Answer:

A. Only certain molecules are allowed to pass through.