A:①
B:①②
C:②③④
D:①②③④
一Don't worry about your trip to the US. I'll be with you all the way.
一OK. Thank you. It'll be my first time to travel abroad.
把圆皮豌豆和皱皮豌豆杂交,F1全是圆皮豌豆,F1自交,F2中皱皮豌豆1 851株,则理论上圆皮豌豆有( )