on sale后面加什么介詞

　　The new stamps are now on sale at main post offices.

　　新郵票現在各大郵局有售。

　　And they are not on sale at your local department store.

　　它們不是你那里百貨商店的銷售品。

　　He bought a sports jacket on sale at Gowings Men's Store.

　　他在高英斯男裝店買了一件打折的運動上衣。

　　Today is Mother's Day and all the jewellery is on sale at Rich's.

　　今天是母親節，瑞奇店的所有首飾全部折價出售。