下列哪种类型不属于以DNA为靶点的致突变
A.烷化剂作用
B.碱基类似物取代作用
C.嵌入剂作用
D.对DNA合成酶系的破坏作用
E.对碱基结构破坏作用
参考答案:D
It was at the airport _____ was completed last year _____ he worked as a volunteer helping foreigners in need of translation service.
A.which; where
B.that; where
C.which; that
D.where; what
下列配备方式中,成本最高的是()
A.购买通用会计软件
B.自行开发
C.委托外部单位开发
D.企业与外部单位联合开发