Điền vào chỗ trống từ thích hợp để hoàn thành câu

You ____________ in school library yet 
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25 điểm
have studied
haven't studied
hasn't studied
didn't study
We protected the country from foreign __________ - such as French, American troops many years ago 
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25 điểm
boss
invaders
winners
loses
Duong Trung Quoc is one of famous Vietnamese ________  who know a lot about festivals in Viet Nam.
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25 điểm
staffs
chairmen
historian
historians