题目

HIV病毒生存和复制的场所必须是（  ）            A． 含多种无机盐的培养液             B． 富含有机质的环境         C． 固体培养基                       D．生物体的活细胞内 答案：D There is a bird in the tree. It is singing. （选出与划线部分意思相同或相近的选项。） A. There is a bird sing in the tree.     B. There is a bird to sing in the tree. C. There is a bird singing in the tree.  D. There is a bird is singing in the tree.