Answer:
A. doubled
Step-by-step explanation:
In the past 20 years, the average size of farms in the US has doubled. The main reason for this has been the development of new agricultural technology. In the past, the size of farms was determined by the amount of work that a family could handle. This limited the extension of a farm, as very large farms would require many employees and would be difficult to manage. However, new technology has meant that farms can now be operated with less people. This has allowed farms to grow in size.