题干
He was about to go out for a walk _____ his teacher came to visit him.
A：while
B：which
C：whe
D：the
答案(点此获取答案解析）
C
A：while
B：which
C：whe
D：the
数变为
．已知每只灯的额定电压为220V，则通过每只灯泡的电流为
