Reaction time is the lapse of time between muscular movement and external stimuli

This statement is true. Reaction time is a skill-related fitness component that refers to the ability of the body to react to external stimuli and make quick decisions on what to do with those stimuli. A good example of this is when your hand accidentally touches the fire of a burning candle. Motor neurons send signals to the brain that trigger a response where you suddenly remove your hand from the source of pain. For exercise activities, reaction time is seen in athletes who are waiting for the gun start. 

Your answer is  d.)relationship between pressure and air volume and led to the understanding of how respiration works

This is true! hope this : ))