DNA连接酶的功能是()
A.使子链与母链间形成氢键
B.使黏性末端之间形成氢键
C.将两DNA末端间的缝隙连接
D.A、B、C都对
参考答案:C
—Peter, you look so tired and wet all over!
—Yes, all afternoon I ________ football on the playground.
A.am playing
B.have been playing
C.played
D.have played
什么是恒重?