There is no doubt _______international cooperation is the key to dealing with cyber crime.

A．then

B．that

C． wheather

D．this

燥之与湿，有霄壤之殊。燥者，天之气也；湿者，地之气也。水流湿，火就燥，各从其类，此胜彼负，两不相谋。《秋燥论》