double limiting

例句：

1. 1. Theprice of the product has doubled sincelast year.
   该产品的价格自去年以来翻了一番。
2. 2. He doubled his efforts to finishthe project on time.
   他加倍努力，按时完成了这个项目。
3. 3. She doubled her savingsto buy a new car.
   她加倍储蓄，买了一辆新车。