本人离职的原因是希望在广告业方面有所发展。
15. I left the office on account of the discontinuance of the business.
本人离职的原因，系因该公司即将倒闭。
16. I now wish to enter an office where the work requires greater individual responsibility and judgment than here,and where there is more opportunity for advancement.
目前，本人希望进入一家可以担负较大责任的公司，并希望能提供升迁机会。
17. One reason that I would like to be employed with your firm is that you are dealing with import and export trade.I would look forward to dealing with oversea companies and at the same time having a chance to use English more.
贵公司主要做进出口贸易是本人欲在贵公司工作的原因之一，我渴望能同外国公司做生意，并借机锻炼英文。