题干

同一品种的结球甘蓝,在北京栽培,长成的叶球约重l﹣3千克,引种到西藏后,叶球的重量普遍增加,最大的竞达6.5千克,当再引种回北京,长成的叶球又是约重l﹣3千克,此现象说明了甘蓝叶球大小这一性状(  )

A:会遗传但不会变异

B:不会遗传也不会变异

C:是由遗传物质改变引起的可遗传变异

D:是由环境变化引起的不可遗传变异

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答案(点此获取答案解析)

D

同类题5

    Have you ever stayed in a hotel? Most Chinese hotels often provide guests(客人) with things like disposable (一次性的) toothbrushes, toothpaste, shampoo and slippers. Many guests like the idea because they don't have to bring their own. But, if you travel to Beijing, remember to bring your own things. Starting from June, some hotels in Beijing will no longer provide guests with these disposables. They want to ask people to use less disposable things.
    Many disposable things are made of plastic. People throw them away after only using them once. It is a waste of natural resources (资源) and is very bad for the environment. Do you know, one Chinese person makes as much as 400kg of waste a year! Most of that waste comes from disposable things. In Beijing, people throw away about 19,000 tons of plastic bags and 1,320 tons of plastic lunch bowls every year! Plastic can take between 100 and 400 years to break down. So the less plastic we throw out, the better. So, wherever you travel, bring your own things and use them again and again.
    Back at home and school, you can also do something to make our world a better place. Try to do these things in your daily life:  Use cloth shopping bags, not plastic ones. After using a plastic bag, wash it out and let it dry. Then you can use it over and over again. Do not use paper cups. At your school dining-room, use your own bowl and chopsticks instead of disposable ones.
    To protect our environment and our home, it is very necessary and important for us to save natural resources.