ph.

1. You're flogging a dead horse by asking him to lend you money.
你向他借钱是白费力气。

1. 徒劳无益：beton paint 混凝土用涂料 | flog a dead horse 徒劳无益 | acidur 阿西杜尔铁硅合金

2. 枉费心机：to eat one's cake and have it又要马儿好,又要马儿不吃草 | flog a dead horse枉费心机 | live on air喝西北风过日子

3. 徒劳;白费力气;事后再做无益的议论：38. fish out of water.离水之鱼;不得其所;感到生疏,不适应. | 39. flog a dead horse.徒劳;白费力气;事后再做无益的议论. | 40. fly in the face of 公然违抗;悍然不顾.