on the trail

追踪

on the eve of..., on the first try, on the ground that, on the grounds of, on the impulse (of...), on the increase, on the lips of, on the nail, on the other hand, on the part of, on the point of, on the principle of, on the quiet, on the road, on the run, on the side, on the sly, on the spot, on the stroke, on the table, on the trail of sb., on the turn, on the verge of, on the whole, on time, on to, on top of, on top on, on trust, on view, on-line, on-stage, on-the-spot, once, once (and )for all, once a month, once and for all, once for all, once in a while, once more,