“一关四检”中的“四检”指对出入我国边境的外国人进行（）
A.安全检查
B.边防检查
C.卫生检疫
D.动植物检疫
参考答案：A, B, C, D
Every necessary means____ to protect milu deer which____ very valuable to us. As a result, the number of milu deer is increasing.
A．are used; is
B．is being used; is
C．have been used; are
D．has been used; are
家禽发生马杜拉霉素中毒的主要原因是（）和（）。
