奶牛慢性子宫内膜炎，表现为（）。
A.有明显的全身症状
B.自阴门流出混浊渗出物
C.妊娠后期流产
D.卧地时自阴门流出多量渗出物
参考答案：B, D
Only after her mother came to help her for the first few months ______ to begin her project.
A．did she allow
B．had she allowed
C．was she allowed
D．is she allowed
在802.45.4定义中的器件有（）
A.FFD
B.FPD
C.RFD
