cells shed (脱落) by people or pets.

　　"While the findings are amazing," says Mitchell Lazar, another study author, "these findings need to be taken as very preliminary." Indeed, he adds several cautions about how the findings should be understood. "For one thing, people eat these fats in foods all of the time. That is likely to be a lot more than would be consumed from indoor dust," he said.

8．What can be concluded from the research?

　　A．Dust harms people's health.

　　B．Dust can help people lose weight.

　　C．Dust is a cause for some diseases.

　　D．Dust may have something to do with weight.

9．What do we know about PPAR­gamma 1?

　　A．It comes from dust.

　　B．It leads to weight gain.

　　C．It can help get rid of dust.

　　D．It only appears in human bodies.

10．The underlined word "preliminary" in the last paragraph can be replaced by "______"．

　　A．limited　　　　　　　 B．important

　　C．misleading D．unbelievable

11．What's the best title for the text?

　　A．Can house dust make us fat?

　　B．Why is it important to clean?

　　C．Anything to do to deal with dust?

　　D．What is the best way to lose weight?

　　We spend around one third of our lives in bed, and the body does a lot of its repair work as we sleep, so enough good quality sleep is very important to our health.It doesn't stop there, though-some sleep positions are healthier than others.So which sleep position is the healthiest?

　　Sleeping on your back is the healthiest sleep position.Health benefits include avoiding back and neck pain.Because the head is raised above the stomach when you sleep on your back, this position is best for people who suffer from nighttime acid reflux (胃酸逆流) as well.Around 80% of heartburn (胃灼热) sufferers have problems during the night, so sleeping on their back could help a lot of people to enjoy a good night's sleep.If the sleep position alone is not enough to alleviate the condition, try raising the head of the bed by up to 4 inches by placing blocks under it.

When you sleep on your back, your face is in a natural position.This means less wrinkles (