若集合M={a,b,c}中的元素是△ABC的三边长,则△ABC一定不是( )
A:锐角三角形
B:直角三角形
C:钝角三角形
D:等腰三角形
下图所示五种基本地形名称从左至右正确的是
— How old is Mr. Gao?
— He is more than thirty. I think he was born _________.