乳牙常见的萌出顺序（）
A.A→B→C→D→E
B.A→B→D→C→E
C.A→B→C→E→D
D.A→B→D→E→C
E.A→C→B→D→E
参考答案：B
Don't worry. They'll come to help us _______.[ ]
A. in half an hour
B. in a half hour
C. after half an hour
D. after a half hour
队员职责是什么？
