题目内容：

[单选题]A．

H．ello，everyone! It's that time of year again! Hualin's fantastic sale! You name it， and we have it at a very good price． Do you like them at low prices? We have sweat-ers in all colors at 50 yuan each! Do you need a bag for sports or school? We have great .bags for just 6 yuan! For young boys and girls， we have T-shirts in red， green，yellow， orange， blue and black for only 15 yuan! And socks in all colors for just 1yuan! And that-s not all． Can-t you believe it? Come down to Hualin and see by your-self!( )21． This passage is_________

A． a story

B． an advertisement(广告)

C． about family

D． about buying and selling