We're in class. You'd better not _______. [ ]
A. talk
B. talking
C. talked
D. to talk
答案:A
()米以下机动船不强制要求在航行中配备并开启第二盏后桅灯,但可以这样做。
A、20
B、50
C、60
D、100
我国成人氟的适宜摄入量(AI)为()。
A.0.5mg/d
B.1.0mg/d
C.1.5mg/d
D.2.0mg/d
E.2.5mg/d