Definition: to be something that has never happened before Level: C2
人类登月是太空史上的首次。
Man walking on the moon ___was ___a ___first in space history.
可重复使用火箭的成功发射是航空航天业的首次。
The successful launch of the reusable rocket ___is ___a ___first for the aerospace industry.
她被任命为CEO是公司历史上的首次。
Her appointment as CEO ___was ___a ___first in the company's history.
