题目

It takes a special person to see a life in danger and go out of his way to make a difference. But that’s exactly what Kole Devisscher did when he _________ the thin ice of a river to save 10-year-old Chartrand from _________ .The young man was _________ for his bravery by MP Joy Smith. Smith _________ him with a certificate and said Devisscher would be nominated (提名) for the Governor General’s Medal of Bravery.Describing the _________ , Devisscher said he thought it was something _________ when he saw a blue jacket in the river. _________ for Chartrand, the teenager decided to back up 已知最简二次根式与是同类二次根式，则a的值是（    ）。A．-2         B．2        C．4         D．-4