OG-8 it 的指代

motorola00

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

Choices A and B incorrectly use the plural verb are with the singular noun equipment. In B, C, and E, when used by does not parallel amount... used by and nonsensically suggests that the people are used by the equipment. D, the best choice, correctly parallels the amount... used by with that used by, in which that is the pronoun substitute for amount. Moreover, D solves the agreement problem of A and B by omitting the to be verb used with visible and placing visible before equipment’, the phrase visible equipment is also parallel with unobtrusive equipment.

答案B,C,E中 it 的这种用法可以吗？（如果不考虑when的错误的话）

super_lee

不行~~~

单数that
复数those

motorola00

it can refer to " the ammount" ?

Samson2004

以下是引用motorola00在2003-12-14 0:57:00的发言：
it can refer to " the ammount" ?

Yes, it is true that it refers to the amount. However, does the amount refers to the amount...used by visible equipment or the amount...used by unobtusive equipment?
If the former, this sentence does not make any sense. If the latter one, these two amounts are different stuffs that cannot be substituted by the pronoun it. In such kind of comparison, that is precise.

motorola00

Great answer! Thanks!

"It" refers to the same thing, and "that" refers to the logical equavalence. There is the similar situation in OG 19.

super_lee

以下是引用motorola00在2003-12-14 0:57:00的发言：
it can refer to " the ammount" ?

it 要代只能代the amount of energy used by equipment

solome

以下是引用super_lee在2003-12-14 22:51:00的发言：
  
it 要代只能代the amount of energy used by equipment

agree