不知道对方姓名、职位等信息时称呼可以用 Dear Sir or Madam, 或To Whom It May Concern； 知道对方的身份
或姓名时，称呼可以用Dear Mr./Mrs. + 姓， 或Dear+ 职位,如：Dear Professor, Dear Mr. Smith, ; 如果是给熟悉
的人则可以用Dear + 名， 如：Dear Jim/Betty.
Yours,/Yours truly, / Yours sincerely, 等
署名：位于结束语下方。考研作文不允许署真名，题目中一般要求签名为“Li Ming”或”Zhang Wei”
Being a senior student in this university, I am writing this letter with the hope of improving the students’ physical condition, as a growing number of students are getting much fatter, according to the latest survey.
Here are some suggestions I would like to put forward. First of all , greater attention should be attached to the physical condition of college students, and I hope you could play a vital role in spreading such an idea. Mean while, more sport apparatus and sport fields may be needed, as more students have enrolled in this great university year by year.
I do hope you can take the above suggestions into consideration and thanks in advance.
Dear Mr. Smith,
On behalf of the Student Union, I am sending this e-mail to you to invite you to act as our judge of English speech contest to be held in our university on June 5.
To be more specific, our contest is on the topic of how to embrace tough challenges in this digital era. During this competition, ten participants will deliver their speeches with respect to this topic. It is widely acknowledged that you are a top expert in this field, so we sincerely hope that you can accept our invitation. For further information, please call me at 9999999.
We are looking forward to your reply and arrival.