I am sure he did not know that his brother graduated with flying colors. A. He cannot have known that his brother graduated with very high marks. B. He may not know that his brother is flying

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

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

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

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