The answer is letter A.
Smooth
muscles are muscles that perform involuntary contractions within the body and
are mainly found in organs (e.g. intestines, liver). Heartbeats are not a
function of smooth muscles, they are the function of cardiac muscles. Cardiac
muscles refer to the muscles of the heart that play a vital role in pumping
blood throughout our organ systems. Among all the muscle groups, the cardiac
muscles are the ones exerting the most effort since the day that you were
conceived up until the day that you die.
