Answer: A) channels formed by integral proteins.
Water molecules and small ions enter a cell through channels formed by integral proteins.
Explanation:
A protein channel is the protein that helps in transporting the water molecule and small ions through the cell membrane. Aquaporins is the integral pore protein that is responsible for transporting the water molecule inside the cell membrane.
It only transport water molecule avoiding other ions. Due to the water transport job it is also called as the water channel in the cell.
