I am sure he did not know that his brother graduated with

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I am sure he did not know that his brother graduated with flying colors.

He should not have been envious of his brother's achievement.

He cannot have known that his brother graduated with very high marks.

That his brother graduated with flying colors must have been appreciated by him.

He may not know that his brother is flying gradually up in a colorful balloon.

Giải thích

Đáp án B

Cách dùng động từ khiếm khuyết “cannot have + Vp.p” để diễn tả một sự suy đoán về một sự việc đã xảy ra: “chắc là đã không làm điều gì”.

Cách dùng này hợp ý nghĩa với câu cho sẵn: “Tôi chắc rằng anh ấy không biết là anh trai của anh ta đã tốt nghiệp với hạng danh dự”.