[問題]考古題form 16 題號14 (structure)

[cecilia1211]

Nearly all trees contain a mix polymers that can burn like petroleum ------properly extracted.

a)after
b)if
c)when it
d)is

答案是b 為什麼不是c阿 ??

謝謝

[pohanchiu]

b) if (it is) properly extracted.

[best555tw]

it 應該代表a mix polymers
所以C的extracted是被動
要在加is