The most important thing we should pay attention to is the thing I have said.
A. which that
Bthat which
Cwhich which
D. that that
网友回答
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。