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An Oceans Vacuum
There's a collection of plastic trash in the middle of the Pacific Ocean．It's bigger than Texas and growing．The way to clean it up now is to catch it with nets．That is both costly and slow．Instead，the Ocean Cleanup Project proposes 62﹣mile﹣long floating barriers that would use natural currents to trap trash．If next year's trials succeed，a full cleanup operation would aim to start in 2020．It could reduce the trash by 42% over 10 years．
Easy﹣On Shoes
In 2012，Mathew Walzer，a high school student with a disability，sent a note to Nike．"My dream is to go to college，"he wrote，"without having to worry about someone coming to tie my shoes every day．"Nike assigned a design team to the challenge．This year，they came out with their solution：the FlyEase．The basketball shoe can be fastened with one hand．A pair of Nike FlyEase shoes sells for $130．
An Airport for Drones（无人机）
As Amazon，Google，and others get ready for drone delivery service，there is one big question：what kinds of home bases will their drones have？Rwanda，in Africa，may have the answer．There，workers will soon start work on three"drone ports"．The goal is to make it easier to transport food，medical supplies，electronics，and other goods through the hilly countryside．Construction is set to be completed in 2020．
21．What's the advantage of the Oceans Vacuum？
A．It can be a money﹣saver.
B．It can grow year by year.
C．It can tear plastic into pieces.
D．It can be put into wide use soon.
22．What do we know about Nike？
A．It offers free shoes to the disabled.
B．It is designing new shoes frequently.
C．It provides customer﹣friendly services.
D．It responded to Matthew's request passively.
23．Why is Rwanda setting up"drone ports"？
A．Because road travel there is rough.
B．Because there are too many drones.
C．Because they're easier to construct than roads.
D．Because they are receptive to new technology.
