I believe the answer is: influence a number of other workers to work harder
Answer:
Trace elements are required by the human body in very minute quantity. Some of the examples of trace elements are iron and copper.
These elements acts as catalyst for the various types of reactions that takes place in the body. Iron is taken in body by diet that we eat. It is found in green vegetables and acts as an important constituent of the hemoglobin which helps in the transport of oxygen.
Copper is also taken inside the body by the food that we eat.It helps in iron absorption, prevent cardiovascular diseases, increases immunity.
Hence, trace elements is equally important as like that of major elements of the body.
Stretching increases flexibility, sit-ups are for abdominal endurance, and distance running are for leg muscle endurance, so the correct answer is pull ups.