题目

读下面的一篇短文，然后根据短文内容，将问题的最佳答案填写在题目前的括号里。 Sally was a student. It was going to be her mother’s birthday. She wanted to buy her a present that would be nice and useful but not expensive. A week before her mother’s birthday, she went shopping after a quick and simple lunch. When she had been looking for half an hour, she found a shop that was selling cheep umbrellas（伞）, and decided to take a black one, since her mother had lost hers the month before. She thought, “You could carry that when you are wearing cl 挤牛奶的女工常与患牛痘的奶牛接触，她们手上会出现牛痘脓疱，但在天花流行时，却从不感染天花。这种免疫物质的产生与下列哪种细胞器的关系最密切 Ａ．线粒体       B．内质网        Ｃ．高尔基体      D．核糖体