{$mEDiAurl} whAt DoEs thE mAn mEAn whEn hE sAys this:
A、hE wAnts to ChAngE thE topiC oF thE tAlk.
B、hE wAnts thE proFEssor to ElABorAtE on A point in thE lECturE.
C、hE is trying to rEmEmBEr somEthing thE proFEssor AlrEADy sAi
D、
D、hE wAnts to CorrECt somE mistAkEs thAt thE proFEssor mADE.