题目

                               If you have ever been rock climbing, then you will know that it is not a very easy sport. In fact you probably felt quite defeated when you first tried to do any serious climbing. Indoor and outdoor rock climbing are both extremely demanding and, like anything else, require practice, to get good at. What most people don’t know is that the sport of rock climbing is one of the most physically and mentally demanding sports there is. There are three basic types of rock climbing. Top roping is probably one of the most common types and i已知某一动物种群中仅有Aabb和AAbb两种类型个体，Aabb∶AAbb=1∶1，且该种群中雌雄个体比例为1∶1，个体间可以自由交配，则该种群自由交配产生的子代中能稳定遗传的个体比例为                                                （   ） A．1/2                B．5/8                C．1/4                D．3/4