—We just had a terrible accident.
—________But it's good to see you are all right.( )
A:Take it easy.
B:I'm sorry to hear that.
C:Don't be afraid.
D:It doesn't matter.
“Do be a ____ (help) person!” my father always says to me.
下列属于海洋自然灾害的有( )
①风暴潮灾害、海浪灾害、海冰灾害、海雾灾害、飓风灾害
②地震海啸灾害、赤潮、海水入侵、巨浪、溢油灾害
③风暴潮灾害、海浪灾害、干旱灾害、海冰灾害、海雾灾害
④地震海啸灾害、赤潮、海冰灾害、巨浪、溢油灾害
已知关于x的一元二次方程:ax2+bx+c=0,若a-b+c=0,则此方程必有一个根为( )