智齿拔除的适应证有哪些()
A.牙位萌出不正
B.冠周炎反复发作
C.无对合牙
D.已经或可能使邻牙龋坏
E.无局部麻醉及拔牙禁忌证
参考答案:A, B, C, D, E
---Has your father returned from Africa yet?
---Yes, but he ____ here for only three days before his company sent him to Australia.
A.was
B.has been
C.will be
D.would be
闸阀具有阻力小、启闭力较小、燃气可()等优点。
A、循环流动
B、自然流动
C、正向流动
D、反向流动