The answer is option D "Machines have replaced much of the manual labor once needed to run a farm."
Explanation:
* Progress in Engineering: This simply means how technological machines like heavy tractors which are now used and are helpful in farming are evolving, meaning they are being used in a larger quantity now.
* Natural Environment: This is the normal way of life or doing things which individuals find themselves practicing in a particular society and at a particular point in time.
* As a result of the machines being developed as an Engineering progress which serves the work of people on the farms, there tends to be less manual labor that would be initially required to run a farm. The machines are now serving the work of human beings (laborers) now.
