Even in Years When Unemployment Is High and Millions of Americans

Even in years when unemployment is high and millions of Americans are looking for work,thousands of jobs every year go unfilled by Americans in the farm industry.Which is the best explanation for this phenomenon?

A) Large farm employment states discourage migration into their states.
B) Regulations prevent farmers from hiring Americans to work on farms.
C) Farmers do not advertise the availability of farm jobs.
D) Americans appear to be unwilling or unable to work on farms.
E) Americans do not have the educational skills required for farm work.