坎井由（ ）部分组成。
A．立井
B．暗渠
C．明渠
D．坎井
E．涝坝
参考答案：A,B,C,E
AIDS is said __________ the biggest health challenge to both men and women in that area over the past few years.
A．that it is
B．to be
C．that it has been
D．to have been
黄酮又叫黄碱素，其弱碱性来源于（）
A.5位OH
B.7位OH
C.苯环
D.1位氧原子
E.吡喃酮环
