题目

Years ago my husband and I were in Acapulco, Mexcio, and we wanted to go to the local open-air market, “Mercado”, but the taxi took us to Walmart. When we told him that we wanted to go where the locals shopped, the driver took us to Safeway, a supemarket. I explained that I was a cook and wanted to see local fruits, vegetables and spices at a big open-air market. He said it wasn’t safe but he’d drive by so we could look from the taxi. We were going to miss the adventure across the street. But, when the taxi stopped in traffic, we got out and began an afternoon of exploring. Af3．一株基因型为YyRr的黄色圆粒豌豆自交，下列说法正确的是（　　）A．后代将出现4种表现型B．后代将出现4种基因型C．后代中绿色皱粒豌豆占$\frac{3}{16}$D．后代基因型为YYRR的占$\frac{1}{4}$