The answer is (A) (11, 4).
Explanation: Given that two vertices of a right-angled triangle are A(5, 12) and B(11, 12).
We can plot the given points on the co-ordinate plane as shown in the attached figure.
We will then see that only the point C(11, 4) will lie exactly below the point B(11, 12). Also, the segment AB and BC are the legs of the triangle, AC is the hypotenuse.
The lengths of the three sides are

Thus, the correct option is (A).