17. If you hope to buy the ideal goods, you should shop around.
想買到理想中的商品，就需要貨比三家。
還能這樣說：
You should inquire the goods at other shops, if you want the dreamed goods.
Shopping around can make you get your ideal goods.
18. She always purchased the goods in good quality and low price.
她總是能買到物美價廉的商品。
還能這樣說：
She always bought goods of high quality and resonable price.
The goods she bought were usually cheap and in fine quality.
應用解析：
put a price on sb. 懸賞緝拿某人；
set at no price 看得不值錢，毫不器重
19. You'd better buy food in supermarket, for the food there is genuine.
買食品類商品最好到超市，那里貨真價實。
還能這樣說：
You'd better go to the supermarket to buy food which is genuine there.
You'd better go to the supermarket to buy food, because the food is genuine there.