大肠埃希菌的RNA聚合酶中具有启动子作用的亚基为（）
A.α
B.β
C.β＇
D.σ
E.γ
参考答案：D
The_________look on his face suggested that he was satisfied with our work. [ ]
A. pleased
B. pleasure
C. pleasing
D. please
