I had just stepped out of the bathroom and was busily drying myself with a towel I heard

问题补充：

I had just stepped out of the bathroom and was busily drying myself with a towel I heard the steps.

A. while

B. when

C. since

D. after

答案：

A. while

(答案→)B. when

C. since

D. after

解析：考查连词：句意：我刚刚走出浴室正在用毛巾擦干自己，这时我听见脚步声。这里是在听到脚步声的那一刻，表示时间点，用when. While通常是表示时间段的，after通常是表示在…….之后。Since后跟时间点时，一般跟现在完成时连用。选B。