--Tom is very stupid. He fails in every exam.

--_____, he is more lazy than stupid.        

A．On the other hand

B．On one condition

C．In my opinion

D．In other words

3月龄鸡，呼吸困难，鸡冠、脚鳞出血，肛门拭子经抗生素处理后接种鸡胚，尿囊液有血凝性。为确定该病原是否为高致病力毒株，OIE规定的试验是（）

A、雏鸡致病力试验

B、鸡胚致病力试验

C、细胞感染试验

D、空斑试验

E、唾液酶水解试验