Substance R is too large to diffuse across the cell membrane or to be transported across by a protein. Molecules of Substance R can, however, cross the membrane and exit the cell. By which of the listed processes do they cross?
A. Active transport
B. Facilitated diffusion
C. Osmosis
D. Diffusion

A. Active transport

Explanation:

The process is called Exocytosis which falls under the Active transport system.

Active Transport describes the processes of moving materials through the cell membrane that requires the use of energy. Substance R was said to be too large to diffuse so it will certainly need some form of energy to make it pass through the membranes. This makes Active transport the correct choice.

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