at half a price/at half price/at a half price哪个是对的哪个是错的...为什

at half a price/at half price/at a half price哪个是对的哪个是错的...为什 in half a price还是 at half a price? 半价用英语是at a half price 还是没有a 价格合理是at a good price还是at good price only students can get it at half price. 同义句 you can get it a 是at a low price 还是in a low price at a good price rationalization at a price 3 half-price Thay are at a good price.这里为什么用的是at? at a price 等于什么 be assessed at a price