A:次级精母细胞核中的DNA分子正好和正常体细胞核的DNA分子数目相同
B:减数第二次分裂后期,细胞中染色体的数目等于正常体细胞中的染色体数
C:初级精母细胞中染色体的数目,正好和DNA分子数目相同
D:任何一种哺乳动物的细胞中染色体的数目和着丝点数目相同
4cm-20mm=____mm
完形填空。
A boy and a girl catch a bird and 1 it in a birdcage (鸟笼). They like it 2 and 3 it every day. A cat sees the bird and wants 4 her supper. 5 the bird is in the cage. She can't catch it. So she is very 6.
One day, she opens the door of the cage 7 wants to catch it. But the bird flies away. The cat 8, and she has 9. The two children 10 and see the bird isn't in. They are very angry and put the cat into the cage.
观察下列各图,找出图中数与数之间的变化规律,那么?处的数是( )