单项选择题

One day an old man went into tile post office. He wanted to posl (寄) a letter. He had never posted a letter be forerc Fie bought a stamp (邮票) and gave it together (一起) with his letter to the girl at the desk. "Oh. no tile girl said. "You must slick (贴) the stamp on yourelf. " He didn’t know where to slick the stamp. so again hc asked the girl. "You may Slick it on yourself. " the girl answered again. Then the man stuck the stamp on the body and went away.
The old nlan went to the post oflqee th order to ______

A. post a lciter
B. buy a stamp
C. see the girl