He was much more thorough in his studies than the rest of his class and it was for this reason（ ）he made such great progress.
A.正确答案Cwhy
B.how
C.that
D.for
He was much more thorough in his studies than the rest of his class and it was for this reason（ ）he made such great progress.
He was much more thorough in his studies than the rest of his class and it was for this reason（ ）he made such great progress.
A.正确答案Cwhy
B.how
C.that
D.for
