Any good mystery must ually uncover a villain, and in a recent documentary, "Who Killed the Electric Car", the filmmakers duly pointed the finger at General Motors. The (62) is not so , but there is little doubt that when GM pulled the plug on its EV1 battery-powered car a decade ago, other (63) followed the Giant carmaker’s lead. Yet GM has now () 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 (65) a prototype that overtakes existing hybrids， (66) Toyota’s Pruis. Today’s hybrids capture energy normally (67) during braking and coasting and use it to power an electric motor that can provide extra bursts of (68) when needed. The Pruis and other hybrids can also run (69) 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 (70) it into the mains (干线). Together with a big battery pack, this provides a much larger range in all-electric (71) , after which the petrol engine kicks in. GM’s car is expected to go around 50 miles (80 km) in all-electric mode， (72) enough for American commuters, who would need to use the (73) engine on longer trips only. The (74) is that plug-in hybrids need a much larger and more costly battery pack． (75) 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 (76) . It is an indication of how the pace is (77) in the race to develop more eco-friendly cars. Others are more (78) . Carlos Ghson, the boss of Renault and Nissan, who is (79) for his skepticism towards hybrids, said he still had doubts that hybrid technology is (80) for the mass market, stressing that plug-in hybrids will have to wait until battery technology improves. Toyota has also been (81) about plug-ins, insisting the Pims’ approach is more convenient.