if XY is the mirror, which among the given options is congruent to the following triangle ABC?
The given triangle ABC is an obtuse-angled triangle.
Option (a), option (b) and option (d) are right-angled triangle, acute-angled triangle and acute angled triangle respectively and hence cannot be the reflection of triangle ABC.
Option (c) is the reflection of triangle ABC.
Option (c), being the mirror image of triangle ABC, is congruent to it.