请问~~~~would的用法

togetherus

Prep 2012 No.51
Reptiles, by drawing their body heat directly from the Sun rather than burning calories to generate it, can
survive on ten percent of the nourishment that a mammal of similar size would normally require.
A. rather than burning calories to generate it
B. rather than the generation of body heat by burning calories
C. and not from generating it by burning calories
D. instead of by burning calories for generating it
E. instead of body heat generated by burning calories
这题选a我明白，可是最后那个would normally require里面的would我不知道是什么用法。
我感觉用would的情况就是
1，在过去的时候表示将来的情况，用would，比如he said he would come.
2,  虚拟语气
请问在这个题目里的would是属于什么情况？
谢谢！

TerraceHo

[by Ron]
"would" has 2 main uses:
（1 * it's the past tense of "will". You can think of it as "a tense that WAS the future, at that time in the past."【would表示過去將來時】
for instance: Jim knows that his son will make the game-winning shot.
this sentence translates into the past tense as
Jim knew that his son would make the game-winning shot.
（2 * it's a CONDITIONAL - i.e., it describes what would occur in some alternate situation that is not actually the case.【would表示虛擬的情況】
for instance: if i were rich, i would buy my own island.

這裡would是第二種用法，表示虛擬情況~