The correct option is A Cisternae, Vesicles, Tubules
The endoplasmic reticulum is composed of the following three kinds of structures:
1. Cisternae.2. Vesicles.3. Tubules. Cisternae are long flattened sacs.The vesicles are oval membrane-bound vacuolar structures.Tubules are branched structure which along with cisternae and vesicles form a network