It seems quite clearly unjust to pay two people different amounts of money for doing the same work. But it is not as easy as it appeals at first （ 1 ） to introduce equal pay for equal work.Two people may be working side by side in a factory and doing the same work, but one may be doing it twice as fast as the （ 2 ） ;or one may be making no mistakes, while the other is making a lot. In some kinds of work, one can solve the problem of speed if one pays by the amount of work to be done and not by the hour: work paid for in this （ 3 ） is called piece-work. But it is not always possible to do this, so it is sometimes useful to pay workers at different rates, which take differences in skill into （ 4 ） . This usually means that the younger and therefore less experienced worker gets less than the_（ 5 ） and more experienced one, which seems reasonable enough.
4. ____

A.other

B.sight

C.older

D.way

E. account