In the past, people didn't use stamps. They had to pay money when they received letters.的意思
问题描述：
In the past, people didn't use stamps. They had to pay money when they received letters.的意思
答
过去的人们不使用邮票，当他们收到信件时，不得不付钱。
答
在过去，人们不用邮票，而是必须在收到信时付邮费。
答
过去,人们不用邮票.他们要在收信的时候付钱