efficiency of is probably the right idiom...
let us think, if the testmaker corrected the idiom error..then how come B is a better choice than A
if i could neglect the idiom error...which i should not but if i do
A & B are comes up
With A there is one problem...
thereby boosting consumption...modifiers the previous clause....
which means that demand will boost consumption.....
Since
B is the given right answer......
i guess authors contended that increasing supply and lowering prices boost consumption......but i guess they have wrongly used WHICH....
WHICH is illogically referring to lowering prices.
or i am missing any rule
X and Y, which boost z.
does which refer to both X and Y ???
Any ideas ?
