Sperm cells bind to an egg via ZP3, a glycoprotein in the glycocalyx of the egg, and can be inhibited from doing so by adding an excess of free oligosaccharide. You are interested in finding the protein on the sperm cell responsible for binding to ZP3. Which of the following is it most likely to resemble?

a. spectrin
b. A porin
c. bacteriorhodopsin
d. A proteoglycan
e. A lectin