题干
_____your composition carefully, some spelling mistakes can be avoided．
A：Having checked
B：Check
C：If you check
D：To check
答案(点此获取答案解析）
C
A：Having checked
B：Check
C：If you check
D：To check
1AB∶1Ab∶1aB∶1ab 
配子间16种结合方式 
子代中有9种基因型 
4种表现型(9∶3∶3∶1)
