[問題]賴水信的高分托福文法p.285Q32

[ministar]

P285 Q32

Diesel engines are highly favored for many purposes because are high in thermal efficiency and
economical of fuel oils.

Ans:C

我知道c是錯的 但是我覺得d也怪怪的
因為of 前面不是要加名詞
economical不是形容詞嗎???

麻煩大大幫我解答一下
謝謝啦

[micki]

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