Group fitness instructors
a. demonstrate proper techniques for yoga and aerobics
b. supervise the rehabilitation of sports injuries
c. manage food service systems for schools
d. teach good health concepts and facts

The answer is option A. The main work of group fitness instructors is to demonstrate how to carry out exercises, such as yoga and aerobics. They instruct and motivate individuals or groups in strength training, exercise activities, and others. They work with people of all skill and age levels.

A. demonstrate proper techniques for yoga and aerobics

A group fitness instructor leads a group of people through the various exercise positions. They also walk around the room giving people helpful hints and helping the clients to maintain the proper position. Sometimes they may even demonstrate modified positions for beginners or experts.