【简答题】下图是某哺乳动物(基因型为 YyRr )的一组细胞分裂模式图。下列有关叙述正确的是 A .甲~丁细胞中发生的可遗传的变异有两种类型 B .乙细胞分裂后将直接产生一个卵细胞和一个极体 C .丙细胞通过异常的减数第二次分裂可形成丁细胞 D .丁细胞形成的原因是减数第一次分裂中有一对同源染色体没有分离
【单选题】Man: Get a move on. We need to be at the airport in an hour. Women: Come on! There's plenty of time. Remember, we're going on this trip to relax, ______.
【简答题】What do you usually do after school? Playing football? Watching TV? Come on, we need something new! Let’s see how kids in foreign countries spend their free time! Mess Around with Dress-up Do your par...