Ais a protein that faces the outer surface of a cell and binds to hormones or other chemical messengers.
a. storage protein
b. messenger protein
c. transport protein
d. receptor

The correct answer is option D, Receptor protein

Explanation:

A Receptor protein is found on the outer side of the cell and they provide receptor sites where a foreign chemical messenger can get associated and perform its function.  As the name also suggest , “receptor” which receives chemical signals from outside a cell. Some common example of receptor proteins are ion channels such as ligand gated ion channels , enzymes etc.

Thus,  it can be a receptor protein which has the ability to bind to hormones or other chemical messengers.

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the answer is either b or c