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The reason why he succeeded is ______ he worked very hard.
A. why B. that C. whether D. how
A．why
B．that
C．whether
D．how
A．why B．that C．whether D．how
The reason __________he succeeded in passing the exam is
___________he worked very hard.
A. for; why B. for; that
C. why; that D. why; how