all the inventions have in common is they have succeeded.A. What; what 　B. That; whatC.

问题补充：

all the inventions have in common is they have succeeded.

A. What; what

B. That; what

C. What; that

D. That; that

答案：

A. What; what

B. That; what

(答案→)C. What; that

D. That; that

解析：考查名词性从句的连接词。What在名词性从句中做主语，宾语，宾语；that在名词性从句中只起连接作用，不充当任何成分，没有任何意思。第一空的what引导主语从句，并在句中做have的宾语。第二空That引导表语从句，在句中不充当任何成分。句意：所有的发明的共同之处是甜蜜都很成功。故C正确。