下列哪项对诊断原发性肝癌有较高特异性（）。

A.B超检查

B.甲胎蛋白测定

C.碱性磷酸酶

D.核素显像

E.乙肝病毒感染标志

—How did you find the talk this morning? 

—______.

A．By asking my students

B．It was easy to find

C．Very disappointing

D．Just in time for it