题干
西葫芦是一种雌雄异花同株的植物，其皮色性状中的黄皮基因（M）对绿皮基因（m）为显性，但有白皮显性基因（W）存在时，基因M和m都不能表达。已知这两对等位基因独立遗传，下列叙述正确的是（）
A：西葫芦皮色能稳定遗传的植株的基因型共有5种
B：基因型为mmW＿西葫芦由于没有M基因，所以表现为白色
C：基因型为Mmww与基因型为mmWw的植株测交，后代有3种表现型
D：基因型为MmWw的西葫芦个体自交，后代表现型比例为9︰3︰4
答案(点此获取答案解析）
C
It is noon now. The sun is high in the sky. It is very hot. Look at the tree. The shadow is short. 
It is evening now. The sun goes down in the west(西方). Look at the tree, the shadow is long again. 
It is night now. The moon is high in the sky. There are some stars in the sky too. 