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______ there will be more green trees than buildings in future cities.

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______ will probably be the fastest and safest means of transport to travel downtown.

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Do you think flying cars will ______ the roads safer?

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______ fossil fuels for transportation and home energy increases greenhouse gases, which makes the globe warmer.

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Humans ______ solar panels on the windows or rooftops of their houses.

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Joe has some solar panels on his house rooftop. He ______ save some electricity from today.

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I don’t think robots ______ skillful enough to keep the streets as clean as humans in the future.

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Different kinds of 3D printers ______ build houses more quickly and cheaply in the next 50 years.