Sun Yang,＿Olympic and world swimming champion of China, has received＿ indefinite ban from competition following his seven-day detention for driving without a license.

A．the; an

B．an;／

C．an; the

D．the;／

皮带太松或滑下的原因是（）

A、轴承弯曲

B、电动机输入电压过低

C、皮带磨损

D、皮带中心轮破损