Which of the Following Best Describes the Function of Gap

Which of the following best describes the function of gap junctions?

A) They occur when peripheral membrane proteins from neighboring cells line up thereby permitting the exchange of water, small ions, and small molecules.
B) They are second messengers that activate protein kinases. The protein kinases then activate or deactivate other proteins.
C) They are intracellular receptors, which associate with signals entering the cell, and often regulate transcriptional processes.
D) They create direct connections between the cytoplasm of adjacent animal cells thereby permitting the exchange of water, small ions, and small molecules.