Answer: c. the Ca2+ ATPase of the sarcoplasmic reticulum
The kind of transport system required to transport Ca2+ throughout the body is the active transport system. The Ca2+ ATPase found in the sarcoplasmic reticulum makes use of ATP as a direct energy source, hence it is classified as a form of active transport.
The glucose-Na+ transporter of intestinal epithelial cells makes use of a concentration gradient that must be created by a different transporter. The system of transport is known as the secondary active transport system. Only the primary active transport system can use ATP as energy.