在过去二十年中用于科学实验的动物数量大大减少了.翻译为英语

The number of animals used for scientific experiment had been greatly reduced during the last two decades.( last score of years, last twenty years.)

In the past twenty years,the number of the animals that are used for experimenting has decreased a lot.

The amount of animals that were used for science experiments have been reduced greatly in the past 20 years.

In the past twenty years, the number of animals used in scientific experiments greatly reduced