Answer:
Protein channel.
Explanation:
Protein channel or channel proteins are present in the plasma membrane that carries the sequence of specific amino acids. These channel proteins are important for the transport of molecules inside the cell.
Generally, hydrophilic and large molecules enter through the channel proteins as their size is large to directly pass through the membrane. The cellular ATP is not required for the passage way of molecule.
Thus, the correct answer is option (D).
