题目

紫茉莉花的红色（R）对白色（r）为不完全显性，下列杂交组合中，子代开红花比例最高的是 A．RR×rr B．Rr×Rr C．rr×Rr D．Rr×RR 答案：DThey play ________, they ________ happy. [　　] A．soccer, are B．the soccer, are C．the soccer, is