题干

音箱装饰布网既美观又能阻止灰尘进入音箱内部,但是它又有不利的一面,对于音箱发出的声音来说,布网就成了障碍物,它障碍了声音的传播,造成了声音失真,有的生产厂家就把装饰布网安装了子母扣,这样听音乐时就可以把布网卸下来,从而获得高保真的听觉效果。听同样的音乐不卸下布网和卸下布网相比较,你认为声音损失掉的主要是(   )

A:高频部分

B:低频部分

C:中频部分

D:不能确定

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答案(点此获取答案解析)

A

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    It may appear strange to hear that crops are making headlines.But this is no ordinary produce—these fruits and vegetables have been grown in simulated(模拟的)Martian and lunar soils!

    Though the possibility of growing crops in outer space only gained widespread interest after Matt Damon grew potatoes in the movie "The Martian",scientists have been testing the idea for many years.Fresh produce will after all be the key to setting up space colonies(殖民地).

    Among the pioneers in this effort is a team led by Wieger Wamelink,a scientist at Netherland's Wageningen University.In 2013,they planted fourteen varieties of plants in simulated Martian and lunar soils.Though the "Mars" plants did not bear any produce,they grew better than the "lunar" plants,most of which died shortly after being planted.Lack of vapor in the soil,according to the scientists,might have accounted for the failure.

    The second experiment began in late 2015.The researchers selected the same crops,while this time they used larger containers and added grass to them.In March 2016,their efforts were rewarded with a variety of produce including the vegetable that kept "The Martian" alive: potatoes.

    However,the researchers were still not sure if the produce was safe to eat.That's because the Martian and lunar soils contain heavy metals like lead and arsenic,which do not affect plants but are poisonous to humans.

    After months of testing,earlier this week,the team finally confirmed that the produce was safe for human consumption.Some of the crops even contained lower levels of heavy metals than plants grown in the "ordinary" earth soil.

    To celebrate the success,the scientists held a dinner party that centered ground the crops.While there is no word on how the food tasted,it sure looks delicious.