It is the test system, _____ the teachers, that is to blame for the heavy burden of middle school students nowadays.

A．other than

B．or rather

C．rather than

D．more than

母牛，4岁，产后2个多月未见发情。直肠检查发现，一侧卵巢比对侧正常卵巢约大一倍，其表面有一3．Ocm的突起，触摸该突起感觉壁厚，子宫未触及怀孕变化。该牛可能发生的疾病是（）。

A.卵泡囊肿

B.黄体囊肿

C.卵巢萎缩

D.卵泡交替发育

E.卵巢机能不全