[ Grammar for TOEFL ]
The professor could not understand _____ most of the students failed the exam despite the fact that the material had been thoroughly discussed in class and additional study sessions were provided.
A. why
B. if they were paying attention during the lectures,
C. while he was explaining the difficult parts,
D. because they seemed well-prepared during the review,

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A. depressing
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Coordinate Conjunction › View
In the example below, what is the coordinate conjunction joining?
Tom will bring the chairs, or Mary can get them from the closet.
A. words
B. phrases
C. sentences/ clauses