Any good mystery must eventually uncover a villain, and in a recent documentary, 'Who Killed the Electric Car?', the filmmakers duly pointed the finger at General Motors. The【C1】______ is not so simple, but there is little doubt that when GM pulled the plug on its EV1 battery-powered car a decade ago, other【C2】______ followed the Giant carmaker's lead. Yet GM has now 【C3】______ its enthusiasm for electric vehicles — or at least for their close cousins, hybrid cars (混合动力汽车). At the upcoming auto show, the company is expected to【C4】______ a prototype that overtakes existing hybrids，【C5】______ Toyota's Pruis. Today's hybrids capture energy normally【C6】______ during braking and coasting and use it to power an electric motor that can provide extra bursts of【C7】______ when needed. The Pruis and other hybrids can also run【C8】______ battery power alone at low speeds over short distances, such as in stop-start traffic. But GM's new car is expected to be a 'plug-in' hybrid, which, as its name implied, can be recharged by 【C9】______ it into the mains (干线). Together with a big battery pack, this provides a much larger range in all-electric【C10】______ , after which the petrol engine kicks in. GM's car is expected to go around 50 miles (80 km) in all-electric mode，【C11】______ enough for American commuters, who would need to use the 【C12】______ engine on longer trips only. The【C13】______ is that plug-in hybrids need a much larger and more costly battery pack．【C14】______ a Pirus to operate as a plug-in hybrid, as some enthusiasts have done, costs around ＄12,000. GM bosses have hinted that his company planned to put a plug-in into mass【C15】______ . It is an indication of how the pace is 【C16】______ in the race to develop more eco-friendly cars. Others are more【C17】______ . Carlos Ghson, the boss of Renault and Nissan, who is 【C18】______ for his skepticism towards hybrids, said he still had doubts that hybrid technology is【C19】______ for the mass market, stressing that plug-in hybrids will have to wait until battery technology improves. Toyota has also been【C20】______ about plug-ins, insisting the Pims' approach is more convenient. 【C1】