几种DNA分子的碱基组成比例如下,DNA的Tm值最低的是
A.A+T=70%B.G+C=20%C.G+C=50%D.A+T=12%E.G+C=80%
参考答案:B
The roof fell before he had time to ________ the room to save his baby. [ ]
A. dash off
B. dash into
C. dash out
D. dash up
整体式箱体时应采用的粗基准是()。
A.顶面
B.主轴承孔
C.底面
D.侧面