请教：PREP I-46

46.   (26975-!-item-!-188;#058&003041)

The continental United States receives an average of 30 inches of precipitation a year; transpiration from soil and from plants returns approximately 21 of the 30 inches to the atmosphere, while the balance of 9 inches contributes to the flow of streams and rivers.

(A) transpiration from soil and from plants returns approximately 21 of the 30 inches to the atmosphere, while the balance of 9 inches contributes to the flow

(B) even though transpiration from soil and from plants returns approximately 21 of the 30 inches to the atmosphere, the remainder of 9 inches contribute to the flowing

(C) although transpiration from soil and from plants return approximately 21 of the 30 inches to the atmosphere, the balance of 9 inches contribute to the flowing

(D) with transpiration from soil and from plants to return approximately 21 inches to the atmosphere, the rest of the 9 inches contributes to the flow

(E) as transpiration from soil and from plants return approximately 21 of the 30 inches to the atmosphere, the rest of the 9 inches contribute to the flow

正确答案：A

(B) even though transpiration from soil and from plants returns approximately 21 of the 30 inches to the atmosphere, the remainder of 9 inches contribute to the flowing   我觉得应该用contributes

(C) although transpiration from soil and from plants return approximately 21 of the 30 inches to the atmosphere, the balance of 9 inches contribute to the flowing  单数

(D) with transpiration from soil and from plants to return approximately 21 inches to the atmosphere, the rest of the 9 inches contributes to the flow             with sth from to 的结构我觉得挺奇怪的 

(E) as transpiration from soil and from plants return approximately 21 of the 30 inches to the atmosphere, the rest of the 9 inches contribute to the flow  单数

你的问题是什么？

这两个分句之间的关系是“不是很紧密的顺承关系”，基本可以看做是个解释说明。看里面的21 of 30和9就知道了。然后表示其它关系的连词都是多余的。while不是转折，是“同时” 的意思。balance不是平衡的意思，是“余额”的意思。

翻译：美国大陆的平均年降雨量是30英寸；大约有21英寸（的降雨量）通过土壤和植物蒸发到大气中，同时剩下的9英寸汇入小溪和河流。