在孟德尔豌豆杂交实验中,若n代表研究的非同源染色体上等位基因对数,则2n代表①F1形成配子的类型数 ②F1形成F2时雌雄配子的组合数 ③F2的基因型种类数 ④F2的表现型种类数
( )There __________ a cat and two dogs in my home. A.be B.is C.are
( )She can't ________ in the lake. A.swimming B.swiming C.swim
( ) What's your _____ fruit? A.very like B.favourite C.much like
( )Lingling is in __________. A.Class Four,Grade One B.Grade One,Class Four C.Class four,grade one
( )Can I have _____ water? A.these B.some C.one