If the angles in a triangle are in the ratio 7:3:4, then the triangle is

Question

$\begin{array}{1 1} (a)\; \text{a right angled triangle} \\ (b)\; \text{an isosceles triangle} \\ (c)\; \text{an obtuse angled triangle} \\ (d)\; \text{an acute angled triangle} \end{array}$