21. The complex numbers $\mathrm { z } 1 , \mathrm { z } 2$, and z 3 ,satisfying ( $\mathrm { z } 1 - \mathrm { z } 3$ )/ ( $\mathrm { z } 2 - \mathrm { z } 3$ ) $= ( 1 - \mathrm { i } \sqrt { } 3 ) / 2$ are the vertices of a triangle which is :\\
(A) Of area zero\\
(B) Right-angled isosceles\\
(C) Equilateral\\
(D) Obtuse-angled isosceles\\