Which of the following is not a controllable health factor?
a. diet
b. infection
c. exercise
d. rest

Infection is not a controllable health factor. The correct option among all the options given in the question is option "b". The other options given in the question is definitely controllable by an individual. Infection can get into a person without his or her knowledge. This infection can be fatal under certain circumstances and so infection always needs to be controlled.

Push up require upper body strength, so weight-training exercises such as shoulder press, curl ups and dead lifts would improve your ability to perform proper push ups.