Sentence Correction

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

[spoiler]What is this second "that" after "underestimate" refering to??????? Also, please discuss each answer choice.[/spoiler]

IMO D,

I think, the second THAT is referring to "The amount of energy"....if u carefully look the parallelism in the sentence u can figure that out...see below

People tend to...Overestimate the amount of light

AND---> parallelism indicator

People tend to...Underestimate THAT (referring--->>the amount of light)

Op A, B, C are redundant...visible equipment should be used instead of equipment that are visible

Op E creates a parallelism error plus awkward (It When construction)...if u say IT refers to The amount of energy okay..

so we have in Op E...The amount of energy WHEN used....doesn't seems good

Edited this post, made a typo error and post Op E as an answer...

IMO D

visible equipment is parallel to unobtrusive equipment

So A,B,C is out and we are left with D and E
In option E "it when" does n't look good.
so D