fall behind not keep up的意思|示意
美 / /
英 / /
落后而不是跟上
fall behind not keep up的网络常见释义
落后 （使）变宽，（使）扩大 fall behind not keep up; be left as in a race 赶不上；落后 Several of the runners fell behind in the race. 有几个赛跑者在比赛中落后了。