Answer:
Elbow
Step-by-step explanation:
Muscle works in pairs and groups e.g biceps flexes the elbow and triceps extend it and it is called antagonistic muscle action.
The working muscle is called the primer mover or agonist. The relaxing muscle by another muscle is called synergists.
When muscles cause a limb to move through the joint range of motion,it could be synergists or antagonists.
I hope this will help you