单选题：根据短文回答题。Home HeatingCentral heating became popular only afte

根据短文回答题。Home HeatingCentral heating became popular only after the Civil War Typically, coat-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 US 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 percent of all energy consumed in the US, has had a commendable (值得赞扬的) efficiency record: from 1978 to 1997, the amount of fuel consumed for this purpose declined 44 percent despite a 33 percent 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 percent over the next two decades that rise is small considering an expected 21 percent 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