Ethanol is more effective at a concentration of 50-70 percent;
乙醇的濃度為50％至70％時(shí)比較有效，
新概念英語(yǔ)第四冊(cè)
Lesson 38 Water and the traveller
?? 句中詞匯解析
從本句中提取的重要詞匯
adj. 有效的;起作用的;實(shí)際的，實(shí)在的;給人深刻印象;
n. [軍]現(xiàn)役兵額，有生力量，精兵;
?? ef出+fect做，制作 +ive形容詞后綴 →做出來(lái)的 → 有效的
"The police bandobast was very effective."
警方的安排十分奏效。
近義：curative, curing, helpful, assistive, operating, operative
反義：incapable, ineffective, ineffectual, inefficacious, inept, inexpert
n. 集中;專(zhuān)心;關(guān)注;濃度;
?? con共同+centr中心+ation后綴→集中；濃縮
"This book requires a great deal of concentration."
這本書(shū)需要全神貫注才能讀懂。
近義：throng, confluence, crowd, heedfulness, application, intentness
反義：dissolution, dissolving, impoliteness, inattention, inattentiveness, absentmindedness
n. 百分比，百分?jǐn)?shù);百分之一;
adj. 百分之…的，每一百中有…的;百分之…支付利息的;
adv. 以百分之…地，每一百中有…地;
?? per貫穿，自始自終+cent一百→百分比
"A conflagration in 1947 reduced 90 percent of the houses to ashes."
1947年的一場(chǎng)大火,使90%的房屋化為灰燼.
近義：percentage, part, portion, fragment, cud, quid