A can do a piece of work in 4 hours; B and C together can do it in 2 hours, while A and C together can do it in 2 hours. How long will B alone take to do it?  Choose the correct choice
A) 12 B) 9 C) 8 D) 6 E) 4
A's 1 hour's work = 1/4 ;   (B + C)'s 1 hour's work = 1/2 ;   (A + C)'s 1 hour's work = 1/2 .   (A + B + C)'s 1 hour's work = ( 1/4+ 1/2) =3/4 .   B's 1 hour's work = ( 3/4 - 1/2 ) = 1/4.   Therefore A alone will take 4 hours to do the work.   4
<result>E</result>
A can do a piece of work in 4 hours; B and C together can do it in 2 hours, while A and C together can do it in 2 hours. How long will B alone take to do it?