震惊世界的奥运会枪杀事件发生在哪届奥运会?()
A.第18届
B.第19届
C.第20届
D.第22届
参考答案:C
The parents suggest_________in the hotel room but their kids were anxious to camp out
during the trip. [ ]
A. sleep
B. to sleep
C. sleeping
D. having slept
NO是大气污染物,但少量NO在人体内具有扩张血管,增强记忆功能。NO难溶于水,通常条件下极易与O2。则实验室收集NO的方法为
A.向下排空气法
B.向上排空气法
C.排水集气法
D.以上方法都可以