题目

How to deal with small fish when catchingLearning how to fish involves more than catching and storing fish. It is often necessary to release a fish, that is, set it free after catching, because it is too small, or you just don’t want to take it home to eat. In some cases, releasing fish is a good measure to keep fish variety and build their population size. 【1】When catching a small fish, do not land it, or pull it out of water. 【2】Hold the fish gently. Do not put your fingers in its eyes. 【3】 It might cause it to develop a disease and reduce its chance of survival.【4】 If the 某种鹦鹉羽毛颜色有4种表现型：红色、黄色、绿色和白色，由位于两对同源染色体上的两对等位基因决定（分别用AA.Bb表示），且BB对生物个体有致死作用。将绿色鹦鹉和纯合黄色鹦鹉杂交，F1代有两种表现型，黄色鹦鹉占50%，红色鹦鹉占50%；选取F1中的红色鹦鹉相互交配，其后代中有上述4种表现型，这4种表现型的比例为：6﹕3﹕2﹕1，则F1的亲本基因型组合是（  ）。 A.aaBB×AAbb       B.aaBb×AAbb      C.AABb×aabb   D.AaBb×AAbb