JAMB 2002 · UME · Q15

The locus of a point $P$ which is equidistant from two given points $S$ and $T$ is

Worked solution (try it first)

Points equidistant from two fixed points $S$ and $T$ lie on the line that cuts $ST$ in half at right angles.
So the locus is the perpendicular bisector of $ST$ , option D.