题目

The workers have torubbish to keep the mountains clean.A. turn up B. give up C. mix up D. pick up 答案：【答案】D【解析】解析：句意：工人为了保持山清洁不得不捡垃圾。A. turn up出现，B. give up放弃，C. mix up混合，D. pick up捡起。根据前后语境及关键部分rubbish to keep the mountains clean可以推测出要想使山保持清洁工人必须捡垃圾．结合选项只有pick up有捡起之意，符合句意。故答案选D。6．两个连续偶数的差是2．