题目内容：

    Cells in our brain usually send a “stop eating” signal when we've eaten enough. But in a study, researchers found that after mice ate fatty food for just two weeks, their brains brake on overeating failed.

Researchers at the University of Washington in Seattle conducted the study.They shared their findings in Science.Garret Stuber is a professor at the University of Washington.He and his team mainly focused on one brain area known-to be connected with eating behavior.This brain area contains many different kinds of cells.Researchers noticed big differences between the glutamatergic nerve cells(谷氨酸神经细胞)of the fat mice and those of the thin mice.And the earlier work by Stuber's group had suggested that these cells act like a brake on overeating.When the researchers stopped these cells from working,mice suddenly overate.They also fattened up. But it wasn't clear how these cells' activity changed as the mice changed from being slim to being fat.

“Being fat doesn't just happen overnight,”notes Stuber.To study that gradual fattening up,his group did a new study.They fed mice with high-fat food.Now and again,they used a microscope to look at how well the animals 'glutamatergic nerve cells could send out signals.During the process,they found the activity of these glutamatergic nerve cells slowed,even before the mice became fat.That cell sluggishness(怠惰)continued as the mice grew larger over a 12-week period.

The results suggest that the high-fat diet is removing the brake on overeating and becoming fat,”says Stephanie Borgland,a professor at the University of Calgary in Canada. Stuber's group doesn't know whether these brain cells will go back to normal if the mice stop eating the fatty food and slim down.It would be hard to keep monitoring the same cells over the months it would likely take for the mice to return to a healthy body weight,”explains Stuber.And it's hard to say whether similar cells control the same thing in humans.

“Having high-fat diets probably affects a much wider family of cells than those studied here,” Stuber notes. “Changes,” he says, “are probably happening across the brain.” Understanding those things might help us find better ways of limiting overeating.

1.What did researchers find in the study?

A.Mice tended to become sluggish if they often overate.

B.Having high-fat diets affected many kinds of brain cells.

C.Mice began to overeat after eating fatty food for a period.

D.The number of brain cells would drop when mice overate.

2.Why was a new study conducted?

A.To prove that fatty food was bad for health.

B.To know more about that gradual weight-gain.

C.To collect more information about the mice 's cells.

D.To observe how long it would take for the mice to grow fat.

3.What does the last but one paragraph mainly show?

A.It's still difficult to answer some questions.

B.It's hard to find the similar brain area in humans.

C.It's wrong to apply what suits animals to humans.

D.It's necessary to keep monitoring the mice for long.

4.Where is this text most likely from?

A.A personal diary.

B.A useful guidebook.

C.A science magazine.

D.An adventure novel