填空题

At Penn State University, engineers have designed aircraft wings that can change shape in different phases of flight, ______.

【参考答案】

just as birds’wings do．
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填空题
Wheels work well on flat surfaces, but are ______.
单项选择题
A．Run later that day.B．Consult a doctor.C．Let her examine his knee.D．Give his knee a rest.
A．Run later that day.
B．Consult a doctor.
C．Let her examine his knee.
D．Give his knee a rest.
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