两对相对性状的基因自由组合,如果F2的性状分离比分别为9:7、9:6:1和15:1,那么F1与双隐性个体测交,得到的性状分离比分别是( ) A.1:3,1:2:1和3:1B.3:1,4:1和1:3C.1:2:1,4:1和3:1D.3:1,3:1和1:4 答案:A6.Dr.Peter Spence, headmaster of the school,told us," fifth of pupils here go on to study at Oxford and Cambridge."( )A.不填;AB.不填;TheC.the;TheD.a; A