keep up是什么意思啊了

　　She is struggling to keep up with her schoolwork.

　　她在努力完成作業(yè)。

　　They were unable to keep up the instalments.

　　他們未能繼續(xù)按時交付這筆分期付款。

　　Things are changing so fast, it's hard to keep up.

　　事情變化得太快了，很難跟上形勢。

　　She did not bother to keep up with the news.

　　她不愿花時間去了解最新消息。