Everyone in the village is very friendly. It doesn’t matter ____you have lived there for a short or a long time.

A．why

B．how

C．whether

D．when

限制性内切核酸酶切割DNA后产生5’端突出的黏性末端，可以用______进行3’端标记；如果限制性内切核酸酶切割DNA后产生3’端突出的黏性末端，可以用______进行5’端标记。