题干
Scott, please remember to ______ the lights when you leave.
A：turn off
B：turn on
C：turn up
D：turn down
答案(点此获取答案解析）
A
Scott, please remember to ______ the lights when you leave.
A：turn off
B：turn on
C：turn up
D：turn down
取何值，分式都有意义的是（ ）。