og 8 中that的用法，还是疑惑，请教

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

D是正确答案，疑问是：

第一个that和第二个that应该在一句话中指代的是同一个事物吧：the amount of energy?

但是第一个that总觉得应该是属于定语从句的啊，所以我考虑非限制定语从句，就会把正确答案给剔除掉，所以第一个that不是定语从句范畴，为什么，相当困惑，3q

这题首先排除BCE,只能在AD中选，A与后面的unobtrusive equipment结构不对称，所以只能选D。我觉得第一个that是非限定性定语从句，而第二个that是指代the amount of energy

能否把原题贴上来？