This is a sufficient assumption question, which means if the new assumption is added, the argument must be absolutely right, and only D can do this, D makes this argument absolutely right.
C should be kicked out immediately, because it has "some", normally only correct in necessary assumption questions.
A is wrong, because it cannot quarantee the righteousness of this argument either.
-- by 会员 s_dUSA (2012/7/22 2:57:38)