计算机辅助设计的简称是
A) CAM B) CADC) CAT D) CAI
参考答案：B
He was so careless that he left _____the door ____.
A．leaving…unlocked
B．to leave…locked
C．left…unlocking
D．leaving…locking
我国实验动物按病原生物学分类有哪几种等级？各表示何意？
