在美国，证券投资基金一般被称为：（）
A.共同基金
B.单位信托基金
C.证券投资信托基金
D.私募基金
参考答案：A
As teachers, we should let our students do ______ to develop their interests. [ ]
A. whatever do they like
B. whatever they are like
C. whatever will they like
D. whatever they like
一般档距导线弧垂相差不应超过（）mm。
A.20
B.30
C.50
D.500
