题干

下列实验现象中,描述正确的是(   )

A:木炭在氧气中剧烈燃烧,生成无色有刺激性气味的气体

B:红磷在空气中剧烈燃烧,生成大量白烟

C:铁丝在空气中剧烈燃烧,火星四射,生成黑色固体

D:水通电分解,生成氢气和氧气

上一题 下一题 0.0难度 选择题 更新时间:2019-10-16 05:20:29

答案(点此获取答案解析)

B

同类题4

质粒是基因工程中最常用的运载体,它存在于许多细菌体内。质粒上有标记基因如右下图所示,通过标记基因可以推知目的基因是否转移成功。目的基因插入的位置不同,细菌在培养基上的生长情况也不同。根据表中的细菌的生长情况判断,目的基因插入的位置是

 
细菌在含氨苄青霉素培养基上生长情况
细菌在含四环素培养基上生长情况

能生长
能生长

能生长
不能生长

不能生长
能生长

同类题5

阅读理解

         A sunflower is a sunflower. A mobile phone is a mobile phone. But can you combine the two to do something for your local environment?

         As early as next year it may well be possible. When you have finished with your mobile phone you will be able to bury it in the garden or a plant pot and wait for it to flower. A biodegradable (生物可降解的) mobile phone was, this month, introduced by scientists. It is hoped that the new type of phone will encourage consumers to recycle.

        Scientists have come up with a new material over the last five years. It looks like any other plastic and can be hard or soft, and able to change shape. Overtime it can also break down into the soil without giving out any toxic (有毒的) chemicals. British researchers used the new material to develop a phone cover that contains a sunflower seed. When this new type of cover turns into waste, it forms nitrates (硝酸盐). These feed the seed and help the flower grow.

       Engineers have designed a small transparent (透明的)window to hold the seed. They have made sure it only grows when the phone is thrown away.

    “We've only put sunflower seeds into the covers so far. But we are working with plant experts to find out which flowers would perform best. Maybe we could put roses in next time,” said one scientist.

        As phone technology is developing so quickly people are constantly (经常地) throwing their mobiles away. This means manufacturers are under pressure to find ways of recycling them.

        Some 650 million mobile phones have been sold this year. Most of them will be thrown away within two years, adding plastic, heavy metal and chemical waste to the environment. A biodegradable cover can offer some relief for nature, according to the scientists.

    “The seed is released and the flower grows in the pot so you don't have to concern yourself with the phone when you have finished using it,” said Kerry Kirwan. She leads the research team, which is based at the University of Warwick in Britain.