【正确答案】 C

【答案解析】[解析] 画线词的原形grasp为动词，意为“抓住”。A项的原形understand意为“懂得；理解”，例：I don't understand your attitude at all.我一点也不理解你的态度。B项have a hold over意为“控制；对……有影响”，例：The officer has kept a firm hold over the soldier.那个军官一直紧紧地控制着那个士兵。C项的原形take hold of意为“抓住；控制住”，例：Mother took hold of the barking dog by its collar.母亲抓住了这条狂吠的狗的颈圈，将它制服了。D项的原形leave hold of意为“放开”，例：She left hold of his hand.她放开了他的手。故选C。