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请选择（49）处的最佳答案
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请选择（47）处的最佳答案
请选择（47）处的最佳答案
What can scientists do now?
What can scientists do now?A．Prescreen a baby's se B．Screen babies for desirable
Older people sometimes know better________
Older people sometimes know better________
Some of the hurdles space tourism faces include a lack of ox
Some of the hurdles space tourism faces include a lack of oxygen and life suppor
请选择（10）处的最佳答案．
请选择（10）处的最佳答案．A．later B．latter C．lately D．afterwards