There is no perfect person, some people have made _____success of themselves in spite of what would appear to be ______ weakness in their professions.

A．/, a

B．a, /

C．a, a

D．/, /

根据连锁遗传现象，可知某两对连锁基因之间发生交换的孢母细胞的百分数，恰恰是交换配子的百分数的（）。