共用题干
第二篇

Home Heating

Central heating became popular only after the Civil War.Typically,coal-burning
furnaces（火炉）fueled the early systems.Natural gas had developed into the leading fuel
by 1960.Its acceptance resulted in part from its wide uses.Because it comes primarily
from U.S.and Canadian fields , natural gas is also less vulnerable（脆弱的）than oil is to
war.Oil remains the most important fuel in a few areas,such as New England.
Electric heating dominates most areas with mild winters and cheap electricity,including
the South and the Northwest.It was made popular at least in the South by the low cost of
adding electric heating to new houses built with air-conditioning.Bottled gas,which is
somewhat more expensive than utility gas,is the fuel of choice in rural areas not served by
utility pipelines.Wood is the leading heating fuel in just a few rural counties.
Home heating,which accounts for less than 7 per cent of all energy consumed in the
U.S.,has had a commendable（值得赞扬的）efficiency record : from 1 978 to 1 997 , the
amount of fuel consumed for this purpose declined 44 per cent despite a 33 per cent
increase in the number of housing units and an increase in house size.The
U.S.Department of Energy,however,forecasts that energy used in home heating will rise
by 14 per cent over the next two decades.That rise is small considering an expected 21 per
cent increase in the number of houses and the trend toward larger houses.
Natural gas and electricity will probably dominate the home heating market for the next
two decades.Solar（太阳的）heating never became popular because of cost and limited
winter sunlight in most areas;in 2000 only 47,000 homes relied on it.

Natural gas didn't become the leading fuel until
A:1978.
B:1960.
C:1997.
D:2000.