（全国I卷）24. Let’s learn to use the problem we are facing ______ a stepping-stone to future success.
A. to B. for C. as D. by
（安徽卷）23. Fred entered without knocking and, very out of breath, sank _______ a chair.
A. on B. off C. into D. to
（福建卷）23. A great man shows his greatness _____ the way he treats little man.
A. under B. with C. on D. by
