When I was a little girl, my brothers and I collected stamps for many years. My mother didn't use to work during the week, but she worked in the post office near our house on Saturdays, and she used to bring home all the new stamps as soon as they were issued (发行). On the day of the World Cup football final in London in 1966, we were very excited because England were playing West Germany in the final. When we were having lunch, my mother told us to go to the post office straightaway after the match if England won, but she didn't tell us why. At 2 o'clock my mother went back to work as usual, while the rest of the family were watching the football on TV at home. Although she wasn't watching the match, she was listening to it on the radio. England won 4:2 and so my brothers and I ran to the post office. As we burst in, my mother was standing behind the counter. She was waiting to sell us a very special limited edition with ENGLAND WINNERS on each stamp. We were over the moon. We still have it today，and perhaps it is worth a lot of money.
According to the passage, her mother worked in the post office ______. A during the week B on Saturdays C on Sundays D for six days