题干

下列有关孟德尔豌豆杂交实验的叙述,正确的是                      (  )

A:孟德尔在豌豆开花时进行去雄和授粉,实现亲本的杂交

B:孟德尔研究豌豆花的构造,但无需考虑雌蕊、雄蕊的发育程度

C:孟德尔根据亲本中不同个体表现型来判断亲本是否纯合

D:孟德尔利用了豌豆自花传粉、闭花受粉的特性

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D

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     "You see someone just sitting there, looking like they're stupid," explains teenager Manny Logan excitedly. "You just run up to them, slap(掌击) them and run off. It's funny."

    The 16-year-old Logan was describing "happy slapping". It's supposed to be fun but it's a new problem in Britain. Young people will attack passers-by while their friends record the whole thing on camera phones. It was first reported in south London six months ago. But, the practice has spread to other parts of the country and videos of attacks have become popular on the Internet.

    The young people are called "hoodies" because they usually wear a sweatshirt with a hooded top. The top can be used to cover the head or face.

    One study in England published earlier this year suggested that as many as one in four teenagers is an active offender. That includes both serious crimes and small acts like not paying for a bus ticket.

    The fear of youth crime has left some parts of towns empty of ordinary people.

    So, the British government declared war on public disorder last week. The Prime Minister has supported a decision by the country's biggest shopping centre in southeast of England to ban teenagers wearing hooded tops. The clothing helps troublemakers hide from the centre's cameras.

    This week, the government is going further. It plans to force teenage offenders to wear orange jackets while they do public service. The idea is to shame them in front of others.

    But some teenagers and experts have complained that, in their rush to stop the hoodies, politicians risk tarring all teenagers with the same brush.