A：由受精卵发育成的生物体属于单倍体
B：“猫叫综合症”是染色体结构变异引起的
C：21三体综合症是染色体数目变异引起的
D：产生人类镰刀型细胞贫血症的根本原因是基因突变
在中国地图上，上海在南京的东面，南京在上海的____面。
No one knows for sure why adolescence is unique ____ humans.
Jim records his physical training every time so that he can________it and think about how he should improve it the next day.
