D.C. Council Chairman Vincent C. Gray said Monday night that if he definitely intended to fire schools Chancellor Michelle A. Rhee after becoming mayor, he "would say so." The remark came at a campaign forum in which Democratic mayoral primary challenger Gray was to debate incumbent Adrian M. Fenty. But Fenty did not attend. A chair that was intended for the mayor was occupied by Kate Blosveren, president of the D.C. chapter of Young Education Professionals, which organized the session. From that perch, she asked Gray questions.