问题补充：
He was unlucky because he failed the exam.
A. He was bad because he failed the exam.
B. He was lucky because he passed the exam.
C. He was unhappy because he failed the exam.
D. He was not lucky because he failed the exam.
答案：
A. He was bad because he failed the exam.
B. He was lucky because he passed the exam.
C. He was unhappy because he failed the exam.
(答案→)D. He was not lucky because he failed the exam.
解析：句意：他不幸运因为他考试不及格。unlucky=not lucky不幸运，而unhappy=sad不高兴的，难过的，故选D。
