Terminal cisterns a) are made of smooth endoplasmic reticulum b) store acetylcholine c) are an important link between the nervous system and the muscle cell d) carry the action potential deep into the muscle cell

Are made of smooth endoplasmic reticulum.

Explanation:

The endoplasmic reticulum is one of the most important cell organelle that is present in continuous with nuclear envelope. The two types of endoplamsic reticulum are smooth endoplasmic reticulum and rough endoplasmic reticulum.

Terminal cisterns are the large extended area of the sarcoplasmic reticulum that may surrounds the transverse tubules. They store the calcium in the muscle cells. The terminal cisterns are derived from the smooth endoplasmic reticulum and shows some structural similarity as well.

Thus, the correct answer is option (a).