21．China became the 143rd member of the WTO on December 11, 2001, thus ______ its 15－year wish to join the global trade body.
A. realized B. to realize
C. having realized D. realizing
22．He had little idea of what was going on outside after twenty years in prison, ______？
A. didn’t he B. wasn’t it
C. was it D. did he
