题目内容：

    Engineers in Upstate New York have invented a folded paper device that looks like a decorated art project. But don't be fooled. This is actually a paper-based battery. No, it doesn't look like any of those metal batteries running flashlights or smartphones. In these systems, the battery can be printed on a page. The battery 's power consists of living bacteria.

Paper electronics are simple to make and inexpensive, notes study leader Seokheun Choi, an engineer at Binghamton University. They need no electrical outlet to recharge. They just need more bacteria, which can be found everywhere — including dirty water.

“ Most batteries use chemicals to generate electricity. Substituting bacteria can be an advantage,” Choi says.“They are cheap and self-repairing.” What paper-based batteries won't do is generate much power. They do, however create enough to run small devices in faraway or dangerous places — such as a battlefield . They might also find use in medicine . For instance, they might power tiny sensors, such as the types used to measure blood sugar.

This invention is based on an observation made more than a century ago — that microbes （微生 物） produce electricity as they digest food. Scientists refer to the bio-batteries based on this principle as microbial fuel cells. A fuel cell generates electricity like a regular battery. But a regular battery stops producing electricity when its inner chemical reactions stop. A fuel cell uses fuel that can be refilled. In this case, bacteria serve as the fuel. By refilling more microbes, as needed, scientists can keep these fuel cells running.

Lab tests have shown that the new battery can produce a current. Now, Choi and his team are looking at ways to increase the power. They're studying different shapes and materials for the anode and cathode （正负 极）. They're also looking for the best ways to combine batteries for more power. The beauty of the paper devices is that you can simply fold them to connect them. And they surely will be a trend in the near future.

1.What makes the paper-based batteries different from other batteries?

A.They are mainly used to run smartphones.

B.They use bacteria to generate electricity.

C.They are used to decorate small devices.

D.They take a much shorter time to recharge.

2.What can the paper-based batteries do?

A.Power tiny devices. B.Lower blood sugar levels.

C.Produce much electricity. D.Change chemicals in the paper.

3.What is the fourth paragraph mainly about?

A.The application of the new battery.

B.The characteristics of the paper batteries.

C.The intention to invent the device.

D.The working principle of the invention.

4.What is the author's attitude towards the development of the paper-based batteries?

A.Defensive. B.Optimistic.

C.Doubtful. D.Ambiguous.