down the radio a little—the baby is sleeping.A. TurningB. TurnC. To turnD. Turned

问题补充：

down the radio a little—the baby is sleeping.

A. Turning

B. Turn

C. To turn

D. Turned

答案：

A. Turning

(答案→)B. Turn

C. To turn

D. Turned

解析：考查祈使句。破折号后面表示的是解释说明，是相对独立的句子成分，由此可判断前半句是祈使句，故用动词原形。