The duck is ____ the lake.
A：in
B：on
C：at
选择适合的单词填空：____ (Which/ What) time is it？
Do not ________ late when you go out with your friends, or your parents will worry about you.
已知ab=4，若﹣2≤b≤﹣1，则a的取值范围是（ ）
