某后备母猪,适配月龄时未见发情;体重显著超过同龄母猪,腰粗壮,臀部发达,检查生殖系统发育未见异常。导致该母猪不孕最可能的原因是(2018真题下112) A.
先天因素 B.
营养因素 C.
配种技术因素 D.
环境气候因素 E.
疾病感染因素

A. 对 ...

单项选择题 A. 对 B. 错

古代正史中只有《五行志》中记录自然灾害。

判断题古代正史中只有《五行志》中记录自然灾害。

___ is known to us all is that America is a developed c...

单项选择题___ is known to us all is that America is a developed country ___ the First World. A. Which; belong to B. As;belonged to C. What; belonging to D. It; belonging to