题目内容：
请根据下面短文回答第题： today we are sure that the mail will be sent every day to our door. But in the early days, noone could be sure about where--or when--the mail would arrive.
There is a stump (树桩) of a big tree in the state of Washington. It was once a "post office". Because people needed a place for the mail carrier(信使) to leave their letters, they found a tree at the cross of roads and cut it down ten feet from the ground. Then they hollowed it out and covered it with something. Inside, they put many boxes. Each box had a family's name on it. The mail carrier could leave letters there for everyone.
Even earlier, when there was no post services, people gave their letters to any traveler going in the right direction. Often they gave them to a traveling shoe maker. The traveler might stop in a small hotel and he would leave the letters there. But the letters stayed there until the person to re- ceive them happened to come by and stop at the hotel.today an airmail letter can travel across the world in much less time than that. And you knowthat your letter will go where you want it to go, and when.
What is the text about? A．The uses of a mail box.
B．The early days of the mail.
C．The post service in Washington State.
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