21. Because methane has been one of the fastest-growing green-house gases，and is

third only to?carbon dioxide and water vapor in total volume, changing the

chemistry of the upper atmosphere.

因?yàn)榧淄槭窃鲩L(zhǎng)最快的溫室氣體之一，其總量僅次于二氧化碳和水蒸氣而居第三位，從而

改變了大氣層上部的化學(xué)成分。

22. China's GDP is?second only to?the US. 中國(guó)的 GDP?僅次于美國(guó)排第二。

23. next to oxygen 僅次于氧

24. Even so, most Americans would probably?rate?New Oreleans, San Francisco

higher.

即便如此，多數(shù)美國(guó)人可能會(huì)把新奧爾良、圣弗朗西斯科排名靠前些。

25. Where did you finish in the 100 metres? I?finished first.

你在 100 米賽跑中獲得第幾名？ 我得了第一名。

26. Would you?rank?him among the world's great statesmen?

你會(huì)把他列為世界上偉大的政客么？

27. a tennis player who?ranked third / is ranked third?in the world

一名排名世界第三的運(yùn)動(dòng)員

28. And?behind?Douglass came Elliot, Bruce, and Langston.

排在道格拉斯后面的是艾略特、布魯斯和蘭斯頓。

29. He?placed eleventh/?was placed?eleventh?in the long individual race.

在這次個(gè)人長(zhǎng)跑中他取得了第十一名。

30. My horse?wasn't even placed. 我的馬未獲名次。