GRE逻辑题,

GRE逻辑题,
Between 1970 and 1980,energy consumption by
United States industry peaked and then declined,so
that by 1980 total industrial use of energy was below
the 1970 level even though total industrial output
had grown substantially in the same period.Industry
must have instituted highly effective energy conser-
vation measures in those years to have achieved such
impressive results.
Which of the following,if true,most seriously weak-
ens the conclusion of the argument?
(A) Many industries switched to the greatest extent
possible from high-priced oil to lower-priced
alternatives throughout the 1970's.
(B) Total residential energy consumption was higher
in the United States in 1980 than it had been
in 1970
(C) Many industrial users of energy had paid little
attention to energy conservation prior to 1970.
(D) Industrial output grew less rapidly from 1970 to
1980 than it had from 1960 to 1970.
(E) The industries whose production dropped sharply
during the 1970's included a disproportionately
large number of energy-intensive industries.