Why Are G-Protein Coupled Receptors Often Known as 7TM Receptors $\beta$

Multiple Choice

Why are G-protein coupled receptors often known as 7TM receptors?

A) They have 7 tyrosine-methionine dipeptides in their structure.
B) They have 7 transmembrane $\beta$ -pleated sheets.
C) They have 7 transmembrane $\alpha$ --helices.
D) They have 7 methionine-tryptophan dipeptides in their structure.
E) They have 7 nucleotides attached to their structure.