MICROANATOMY

Detailed explanation-1: -Skeletal muscles only pull in one direction. For this reason they always come in pairs. When one muscle in a pair contracts, to bend a joint for example, its counterpart then contracts and pulls in the opposite direction to straighten the joint out again.

Detailed explanation-2: -Answer and Explanation: Since muscles can only move bone in one direction, they must work in pairs in order to move bones in the opposite direction. This occurs in antagonist pairs.

Detailed explanation-3: -To move the bone in the opposite direction, the relaxed muscle contracts and the first one relaxes. Thus two muscles have to work together to move a bone.