試題詳解

21. Besides the enormous expenses needed to replace the 30 million retiring baby boomers ______ in present-day America - and to keep the inflation rate down, the cost to society will be even greater if the immigration issue is not taken care of at this time and allowed to continue boiling.
(A) who are no replacements
(B) for whom there are no replacements
(C) whom there are no replacements
(D) who replace them