keep up with =catch up with
赶上,这两个的区别在于keep up with,追赶人与被追赶人所处情况差不多,
而catch up with暗示追赶人处于落后地位.
通俗的讲
keep up with 跟着.跟上.保持不落后的状态.
catch up with.赶上.强调要上前赶