Not until we the school for children with disabilitieshow they overcome difficulties

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* Mark the letter A, B, C, or D on your answer sheet to indicate the correct answer to each of the following questions.

Not until we________ the school for children with disabilities________how they overcome difficulties.

had visited/ did we know

visited/ had we known

visited/ did we know

have visited/ did we know

Giải thích

Chọn C Câu đề bài: Mãi cho đến khi chúng tôi đên thăm trường dành cho trẻ khiêm khuyết chúng tôi mới hay về cách chúng đã vượt qua được khó khăn của chính mình.

Đáp án C. visited/ did we know

Not until sb did sth + đảo ngữ: mãi cho đến khi ai làm gì rồi mới...