题目内容
阅读下题，根据括号内的汉语提示，用句末括号内的英语单词完成句子。
Qian Xuesen went to California from 1935 to 1955, ________(在那时期)he concentrated on the research into jet planes．(period)
答案：during which period
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题目内容
阅读下题，根据括号内的汉语提示，用句末括号内的英语单词完成句子。
Qian Xuesen went to California from 1935 to 1955, ________(在那时期)he concentrated on the research into jet planes．(period)