题目

种皮光滑豌豆和种皮皱缩豌豆杂交，F1全是种皮光滑的豌豆，自交后代F2中种皮皱缩的有1850株，则种皮光滑的株数为：   A.5550          B.3700           C.1850           D.7400 答案：A－How much is the pair of shoes?－Twenty dollars ____ enough.A. is   B. are     C. am