题目

婴儿用的一次性纸尿片中，有一层能吸水防漏的物质．下列高分子中有可能被采用的是： 答案：B— Who do you think ________ the book here?  — It may be John. He was sitting here all the morning. [    ]A. was leaving  B. leavesC. had left  D. has left