時(shí)間關(guān)系：at once; immediately; at length; in the mean time; meanwhile; at the same time; in the end; then; soon; not long after; later; at once; at last; finally; some time ago; at present; all of a sudden; from this time on; from time to time; since then; when; whenever; next point; a few minutes later; formerly; as; once; since; occasionally; in a moment; shortly; whereupon; previously