helicopter can take off and land straight up or down, and can also stay
still in air.
A.The; an | B.A; the | C.A; 不填 | D.The; 不填 |
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helicopter can take off and land straight up or down, and can also stay
still in air.
A.The; an | B.A; the | C.A; 不填 | D.The; 不填 |