Nancy hasn’t begun on her PH.D ________ working on her master’s degree.

A. still because she is yet

B yet as a result she is still

C yet because she is still

D still while she is already

下列哪两种药物均有预防局麻药毒性的作用（）

A.安定和吗啡

B.苯巴比妥钠和安定

C.吗啡和阿托品

D.阿托品和苯巴比妥钠

E.安定和阿托品