求助关于代词that不能作主语的问题！！！

yangxu1234

看白勇语法里说的是代词that不能作主语，但是下面这题
8.  Lacking information about energy use, people tend to overestimate the amount of energy used by equipment. such as lights, that are visible and must be turned on and off and underestimate that used by unobtrusive equipment, such as water heaters.


(A)equipment, such as lights, that are visible and must be turned on and off and underestimate that


(B)   equipment, such as lights, that are visible andmust be turned on and off and underestimate it when




(C)  equipment, such as lights, that is visible and must be turned on and off and underestimate it when




(D)  visible equipment, such as lights, that must beturned on and off and underestimate that




(E)   visible equipment, such as lights, that must beturned on and off and underestimate it when

答案选d，可是d里面的两个that不都是主语吗，请NN解答，如果是主语，为什么又可以了，如果不是，那是做什么成分。谢谢！

yangxu1234

多谢两位的解释，似乎有些明白了，能不能这样理解：
第一个that引导定语从句修饰lights，不是代词。
第二个是代词 指amount of energy 但后面的used是分词做修饰语，也就不是主谓结构，that就不是主语。

myungryong

同意ls
还有第一个that是做从句引导词而不是代词
第二个that是做代词 指amount of energy

pansean

句子主干people tend to overestimate xxx and underestimate that,  overestimate与underestimate平行关系
第一个that是代指前面的light, 第二个underestimate that是宾语从句...