A Battery's Nightmare Portable electronics that can be carried about easily are only as good as their batteries   and, let's face it, batteries aren't very good, especially when compared with, say, petrol, which packs 100 times a battery's energy into an equal space. That's why a large group of mechanical engineers (centered at the Massachusetts Institute of Technology, but with partners at other universities and companies) are hard at work in an effort to replace batteries with a tiny engine that runs on fuel. Imagine a battery-free life! When the fuel runs out in your mobile phone, you just fill up and go. The engine---about the size of a ten-cent coin---starts with a combustion chamber   that burns hydrogen. Its tiny parts are etched   onto silicon wafers   in the same manner that computer parts are etched onto integrated circuits  . The first engine is made up of five wafers. And since these wafers could be produced in much the same way as computer chips, they could probably be produced quite cheaply. But the _ in all this nice detail is efficiency. Tiny engine parts don't always behave like the bigger parts of the first engine. Something between the parts can slow down the works, according to Columbia University Professor LucFrechette, one of the engine's designers. Extreme heat from the combustion chamber is also a problem, often leaking to other parts of the engine. The scientists' goal is to create an engine that will operate 10 times better than batteries operate. Frechette says that a complete system, with all parts in place and working, will be set up in the next couple of years, but commercial models aren't likely until at least the end of the next ten years. According to the passage, the title suggests that   _   .
batteries should be greatly improved petrol will be used instead of batteries the time of batteries will be gone forever pollution problems caused by batteries must be solved