The coordinates of the three points A.B.C on the plane are (﹣5,﹣5),(﹣2,﹣1)and(﹣1,﹣2)respectively,the triangle ABC is( )
(英汉小词典:right直角的;isosceles等腰的;equilateral等边的;obtuse钝角的)
A、a right trisngle
B、an isosceles triangle
C、an equilateral triangle
D、an obtuse triangle