21.This is the best hotel in the city ____ I know.
   A. which       B. that         C. where   D. it
22. When spring comes, it gets____.
A. warm and warm          B. colder and colder
  C. warmer and warmer       D. shorter and shorter
23.I'll tell you __________ he told me last week.
 A. all which   B. that   C. all that   D. which