The mirror line X-X is vertical and lies to the right of the figure, so the image is the left-right reversal of the figure. Heights stay the same, and everything on the left of the figure moves to the right in the image. The original is a right-angled triangle with the vertical side on the right, the apex at the top and a curved base. Flipping it gives a triangle with the vertical side on the left, the apex at the top and the long corner at the bottom right. Option 1 still has the vertical side on the right, so it is not a mirror image (it is only a copy). Now compare the inner lines of the flipped figure: a short line starting on the vertical side, a chord from lower on the vertical side rising to the slanted side, a line from the vertical side running down to the bottom-right corner, a line from the apex to the base with a short vertical dotted line near the right, and the curved edges. Option 3 contains exactly these lines at the correct heights. Option 2 lacks the short line on the vertical side and Option 4 has chords meeting the sides at the wrong places. Hence Option 3 is the true mirror image. Answer: (3) Option 3
