Ⅰ.单句语法填空(高考真题改编)
1. (2019年天津卷)The professor warned the students that on no account ________ (they, should) use mobile phones in his class.
解析：句意：那位教授告诫这些学生，他们绝对不应该在他的课上使用手机。此处表示否定含义的介词短语on no account位于宾语从句句首，宾语从句要用部分倒装结构。
答案：should they
2. (2018年全国卷Ⅱ)China's approach to protecting its environment while ________ (feed) its citizens “offers useful lessons for agriculture and food policymakers worldwide，” says the bank's Juergen Voegele.
解析：while后面省略了China is，省略句的原则：在时间状语从句、条件状语从句、让步状语从句中，如果从句的主语和主句的主语一致且含有be动词时，那么可以把主语和be动词一块省略，故填feeding。
答案：feeding
