在RNA生物合成过程中，最不稳定的碱基配对为（）
A.rC－dG
B.rΑ－dT
C.rG－dC
D.rU－dA
E.rT－dA
参考答案：D
_______ is even important is ______ as the earth cooled down, water began to appear on its surface.
A．That, that
B．What, that
C．What, what
D．It, that
简述量变和质变的辩证关系？
