It can be inferred from the passage that early historians of women’s labor in the United States paid little attention to women’s employment in the service sector of the economy because________．
A．fewer women found employment in the service sector than in factory work
B．the wages paid to workers in the service sector were much lower than those paid in the industrial sector
C．women’s employment in the service sector tended to be much more short—term than in factory work
D．employment in the service sector seemed to have much in common with the unpaid work associated with homemaking