题目

My mother loves flowers. As soon as warm weather comes around，you will find her planting，watering and weeding over everything. For many years we lived next door to each other，and she spent as much time in my garden as she did her own. After the flowers became plentiful each summer，she would cut colorful bouquets(花束)to enjoy inside the house－both hers and mine. I would often come home from work and find a beautiful arrangement of fresh flowers on my coffee table. Shortly before Christmas one year，a local flower shop offered a bouquet a month special. It seemed to be a gre将雌果蝇的一个卵原细胞内的全部染色体DNA用15N标记，产生的卵细胞与一个不含15N的正常精子受精，形成的受精卵连续分裂两次，则产生的子细胞中含15N的有A．1或2个B．2或4个C．4个D．不能确定