The most important thingwe should pay attention to is the thingI have said.A. which thatB.

问题补充：

The most important thingwe should pay attention to is the thingI have said.

A. which that

Bthat which

Cwhich which

D. that that

答案：

A. which that

B. that which

C. which which

(答案→)D. that that

解析：考查定语从句。第一空先行词thing前面有最高级修饰时使用关系代词that,第二个定语从句的先行词是不定代词thing，关系代词还是用that指代它。句意：我们应该注意的最重要的事情是我所说的事。