Dear Sir or Madam, Dear teachers, boys and girls, and Dear Grandpas, grandmas, Uncle, Antie.
尊敬的领导，亲爱的老师、同学们以及在座的的各位爷爷奶奶叔叔阿姨。
You can just put "Dear Sir or Madam", and you can write "to whom it may concern".
你可以就写“亲爱的先生或者女士”，也可以写“尊敬的相关人士”。
Dear Sir or Madam: The original and one copy of our leasing agreement1 are enclosed.
简要翻译附上我们租赁合同的原件及一份复印件，请查收。
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