This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Microbiology
The function of B subunit of cholera toxin is ? 
Select and explain. 
A. ADP ribosylation of G protein, B. To bind GM1 ganglioside receptor, C. To stabilize cholera toxin, D. To increase cGMP
B: To bind GM1 ganglioside receptor
Answer: B: To bind GM1 ganglioside receptor 
Explanation: Ans. is `b' i.e., To bind GM1 ganglioside receptor