Car companies are developing vehicles that will plug into electric sockets，just like many laptops，digital cameras，cell phones and Mp4 do．Called“plug-in vehicles”，these cars will get most of their power from electricity. Their drivers won't have to stop at gas stations as often as usual．
The technology is more than just cool. In our car-filled world，plug-in vehicles could reduce the amount of gas we use，which keeps rising in cost now and then. Besides，driving around in these vehicles may even help the environment．Gas-burning cars produce a lot of greenhouse gas，which causes globe warming.
The first company-produced plug-in vehicles could hit the roads by 2010. But engineers still have a lot of work to do to make the technology practical and inexpensive．
Batteries(电池) are the biggest challenge. In the plug-in-vehicle world，Li-ion(锂离子)batteries are getting the most attention．These batteries can store a large amount of energy in a small package，and they last a longer time between charges．Li-ion batteries can fit laptops，cell phones，heart instruments and other similar pocket ones.
But because cars are so big and heavy, it would still require a suitcase-sized Li-ion batteries to power about 12km of driving．What's more，the batteries are much expensive．
“A car filled with batteries could go a long distance，”says Ted Bohn, an electrical engineer in Chicago．“But it couldn't pull any people．and it would cost $100,000．”
So researchers need to work out how to make batteries smaller and cheaper，among other questions.
“The answers don't exist yet，”Bohn says，“As a kid，I thought someone someplace knows the answer to everything．All of these questions haven't been decided．That's what engineering is about-making a guess，running tests and getting fine results．”
72．The passage mainly talks about        of a new car
A．the developing    B．the speed    C．the appearance D．the batteries
72．Which is true according to the passage?
A．The“plug-in vehicles”will use electricity completely as driving power．
B．The new technology will help protect our environment．
C．The technology of using electricity as driving is quite practical now．      
D．The biggest challenge of the new technology is that it will cost us more energy．
74．How does Bohn feel about the future of the technology according to the last paragraph?
A．Confident    B．Puzzled．    C．Worried． D．Disappointed．
75．According to the passage，the new technology is facing the following problems except that ．
A．the new technology cannot come into use at present
B．the cost of the new technology is quite high
C．the government won't support the technology
D． the size of the batteries is too big at present