Answer:
b. enables cell to recognize and respond to external environment
Explanation:
There are two types of receptor present in/on the cell. The receptors that are present on the cell surface are called the cell surface receptor and the receptor which is present inside the cell is called an intracellular receptor.
The cell surface receptor is responsible for enabling the cell to recognize and respond to the external environment. The signal molecules that bind to the cell surface receptors are mostly hydrophilic and they generate an intracellular cascade in the cell which brings specific changes in the cell. So the right answer is b.
