5000 câu trắc nghiệm Tiếng Anh 9 có đáp án - Phần 98

After he had researched and ________ his paper, he found some additional material that

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After he had researched and ________ his paper, he found some additional material that he should have included.

wrote

written

writing

have written

Giải thích

Chọn đáp án B