It's difficult for me to decide which one to choose, because ______ of them are good. [ ]

A. neither

B. both

C. either

D. each

PFM修复体是由下列哪一项在真空炉内烧结而成的修复体（）。

A.高熔瓷粉与镍铬合金

B.中熔瓷粉与烤瓷合金

C.低熔瓷粉与中熔合金

D.低熔瓷粉与烤瓷金合金

E.低熔瓷粉与金合金