fall behind

落后

faith, faith-cure, faith-healer, faithful, faithfully, faithfulness, faithless, faithlessly, faithlessness, fake, faker, fakir, falcon, falconer, falconry, fall, fall apart, fall away, fall back, fall back on, fall behind (sb/sth), fall by the wayside, fall down, fall for, fall for sb, fall guy, fall in, fall in love, fall in love (with), fall in love with, fall in love with sb., fall in with, fall into, fall into step, fall into sth, fall off, fall on one's knees, fall on/upon sb/sth, fall out, fall out of,