一个标准的双链DNA分子的一条链上(A+T)/(C+G)=a，其互补链中(C+G

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问题选择题

一个标准的双链DNA分子的一条链上(A+T)/(C+G)=a，其互补链中(C+G)/(A+T)的比值是 [ ]

A．1/a

B．2a

C．a/2

D．a

答案

答案：A

选择题

When he looked up，he suddenly found himself________by a group of teenagers，________looked at him anxiously.

A．to be surrounded；which

B．surrounded；who

C．be surrounded；who

D．having been surrounded；which

问答题简答题

压力棒曲线牵伸特点。