In december 1999, boris yeltsin resigned as russia's president because

On December 31, 1999, Boris Yeltsin, under heavy internal pressure, announced he would be resigning from his position and leaving the presidency in the hands of the Prime Minister Vladimir Putin. Yeltsin was incredibly unpopular with his people at the time and noted his reason for leaving office was due to failing health. In April of 2007, Yeltsin died of congestive heart failure.

Ithink the answer should be a.