Do you remember ______? [ ]

A. where did you buy the dictionary

B. where you bought the dictionary

C. where do you buy the dictionary

D. where you buy the dictionary

橡胶是重要的工业原料，生胶的弹性好但强度较差，将其硫化后，强度增大，但弹性减弱，且硫化程度越高，强度越大，弹性越差。在以下橡胶制品中，你认为硫化程度最高的是[ ]

A．气球

B．医用乳胶手套

C．汽车外胎

D．橡皮筋