drop structure

例句：

1. 2.
   使
2. 3.
   使
3. 1. The drop in oil prices has had a significant impact on the global economy.
   石油价格的下跌对全球经济产生了重大影响。
4. 2. The company's sales have been dropping steadily since the beginning of the year.
   自年初以来，该公司的销售额一直在稳步下降。
5. 3. The amount of water used has been dropping significantly over the past few years.
   过去几年中，使用的水量显著减少。