题目

--- I bought the digital camera two months ago. --- You mean that you __________ it for two months.     A. have had     B. have been     C. have bought    D. have taken 答案：A 生物工程对遗传物质的改造、组装、和搬移实质上处在何种水平上 [　　] A．细胞水平 B．分子水平 C．器官水平 D．细胞器水平