Directions: The sentence below or part thereof has been underlined. The underlined part may have an error of grammar or diction. Select the option that best corrects the error, if any.

Plights of migrant farm workers, who labour in the vast agricultural fields of America's southern states,historically has been a difficult one.

Plights of migrant farm workers, who labour in the vast agricultural fields of America's southern states, historically has been a difficult one.

Plights of migrant farm workers, who, historically labors in the vast agricultural fields of Americas southern states, has been a difficult one.

Historically the plight of migrant farm workers who labor in vast agricultural fields have been a difficult one.

Historically, the plight of migrant farm workers, whose labor in vast agricultural fields of America's southern states has been a difficult one

Historically, the plight of migrant farm workers who labor on vast agricultural fields of America's southern states has been a difficult one.