Crunches are principally a(n) exercise.
a. abdominal
b. arm
c. back
d. chest

Option A

Explanation: The abdominal part of the body consists of 29 core muscles, which are located mostly in the back, pelvis and abdomen part of the body.

This group of muscles are the base for all the movements that is performed by the human body. The crunches are set of abdominal exercise that helps to strengthen the muscles that can support and protect the back.

It makes the spine less prone to injury. This exercise also helps to reduce the pain while lifting heavy items, turn and twist and many more movements required for daily life.