The correct figure has a quarter-circle arc at its bottom-left corner, a diagonal line running to the top-right corner, a small circle above that diagonal and a short slanting line at the bottom-right corner.

The question figure is symmetric about its vertical middle line, so the missing top-right quarter must be the mirror image of the top-left quarter.

The top-left quarter has: a diagonal from its outer corner (top-left) to the centre, a quarter of the central circle at the corner touching the centre (bottom-right), a small circle above the diagonal, and a short slanting line at its lower outer corner (bottom-left).

Mirroring left to right: the diagonal runs from the top-right corner to the centre, the arc sits at the bottom-left corner, the small circle stays above the diagonal, and the short slanting line moves to the bottom-right corner. Only this answer figure has all four parts in these positions; the others have the arc at the top, no diagonal, or the small circle below the line.