I wasn’t aware of this before, but recent research _____ that eating too much fat can contribute to heart disease.

A．has shown　

B．will show

C．was showing

D．showed

面发育沟大约有“Y”、“H”、“U”形的牙是（）

A.下颌第一磨牙

B.下颌第二前磨牙

C.上颌第一前磨牙

D.下颌第一前磨牙

E.下颌第二磨牙