The nervous system avoids muscle fatigue during submaximal contraction by
a. always recruiting slow-twitch motor units.
b. asynchronous recruitment.
c. synchronous recruitment.
d. always recruiting fast-twitch motor units.

B. Ashchronous recruitment

Explanation:

Asynchronous muscles are muscles that Don't have one-to-one relationship between electrical stimulation and mechanical contraction. Such muscles can be found in About 75% of flying insects and they have convergently evolved 7-10 times.

The synchronous muscles which is their counterparts contracts once per neural signal, but mechanical oscillations trigger force production in asynchronous muscles.

Hence the rate of mechanical contraction is an order of magnitude greater than electrical signals.

Although they achieve greater force output and higher efficiency at high frequencies, they have limited applications because of their dependence on mechanical strength.

The nervous system recruits the Ashchronous muscle to avoid muscle fatigue during submaximal contraction.