题目内容：

The price of this exercise book is the lowest,----- it's the most suitable for high school student,A.since B.while C .as D.when 理由?

优质解答

选B
题干说这本练习册的价格是最低的,是最适合高中生的,这2者应为转折关系.since 为由于,as为因为,when为当...的时候,根据题意选B.
翻译为：这本练习册的价格是最低的,然而却是最适合高中生的.