题目

杂交育种是通过品种间杂交，创造新变异类型而选育新品种的方法．将两个各具有期望的优点的纯合亲本进行杂交，F1自交能产生多种非亲本类型，再经过选育就可能获得符合需要的新品种．下列相关叙述错误的是（ ） A．杂交育种所依据的主要遗传学原理是基因自由组合 B．F1形成配子时，同源染色体上的非等位基因可通过非姐妹染色单体的交换进行重组 C．F1形成配子时，非同源染色体上的非等位基因自由组合 D．杂交育种能定向改造生物性状，育19．假如你是李华，请结合以下要点给某英语网站投稿，向外国朋友介绍自己的家乡．1．家乡基本情况；2．家乡特色．注意：1．词数100左右2．可以适当增加细节，以使行文连贯．参考词汇（be located in…；  cover an area of； have a population of； impress； be famous …；  worth a visit）My hometown．is a mountain village witha history of over 200 years．It has a population of more than 800．It covers an area of 10 square kilometers．People here live in harmony withnature．There is a river flowing across thevillage．When you arrive here，you can enjoy yourself hearing birds singing in trees andwatching fish swimmingin clear water．What impresses you most is probably that theair is fresh to breathe，there is a wide variety of food to taste andthe local customs are unique．This is a dream place for you to get close to nature．All guests are welcome and it is worth a visit．．