A Major Group of G Protein-Coupled Receptors Contains Seven Transmembrane

A major group of G protein-coupled receptors contains seven transmembrane α helices.The amino end of the protein lies at the exterior of the plasma membrane.Loops of amino acids connect the helices either at the exterior face or on the cytoplasmic face of the membrane.The loop on the cytoplasmic side between helices 5 and 6 is usually substantially longer than the other loops.The G protein activated by this receptor most likely interacts with the receptor

A) at the NH₃ end.
B) at the COO^- end.
C) along the exterior face of the membrane.
D) at the loop between helices 5 and 6.