I am Li Ming, your friend. I am writing this letter to put forward my serious suggestion on which subject you are supposed to choose at college. ②第二段提出建议，写明原因。 The suggestion that I provide to you is as follows. As far as I am concerned, it would be helpful for you to take computer science as your major at college due to the fact that there are some difficulties in seeking a desirable job after graduation because of the cut-throat competition in the job market. But as for the graduates of computer science, it is comparatively easy to find a job to support themselves after they graduate. Of course, I would recommend that you keep up your reading of history in your spare time. ③总结建议＋礼貌性用语。 I hope you will find these proposals helpful/useful/conducive. Thank you for taking time to consider my suggestions.