改写以下句子,用含有knock的短语动词代替以下句子中用斜体印出的词组

问题描述:

改写以下句子,用含有knock的短语动词代替以下句子中用斜体印出的词组
1.the shopkeeper (reduced)the price of all his goods by 20%

The shopkeeper knocked off the price of his goods by 20%.