What are the agonist and antagonist muscles of the wrist

"She kept a tight grip on the handles, which throbbed violently with every explosion of the one-cylin­der motor, and as she sheered around bushes and lurched along at a reluctant trot behind her impetuous servant, she looked like a puppy who had grabbed something that was too much for him."

What is the "impetuous servant"?
A.the mower B.the explosion C.the woman D.the small dog