Sitting on a chair all day in school can make anyone want to move around. So, more and more teachers are letting students have a ball. By sitting on exercise balls instead of chairs, teachers find students' posture (姿势) and attention improve.
Dottie Pownall, a fifth-grade teacher in West Virginia, USA, has been using balls as chairs since December 2008. "The students love them", she says. Pownall took a survey of her students. She found that 80% of the students thought sitting on the balls helped them pay more attention to what they were learning.
The teacher, Pisa Witt, felt so strongly about the use of balls as chairs, she started Witt Fitt. This company encourages the use of the balls. And the company educates not only teachers but also students on how to use them. "Our products are used in 24 states, three provinces in Canada, Puerto Rico ('波多黎各) and Japan," says Witt. "Research shows that sitting on the balls makes them sit up straighter. You can slouch (低头垂肩地坐) on a ball," says Witt, "but it feels awful." Because the students are moving, their blood (血液) increases. That carries more oxygen (氧气 to the brain (大脑), so the kids have more energy and can focus longer.
"Furthermore, they're fun." says Pownali.
【小题1】 What will happen if a student sits on a chair all day in school? The student will _________.

---How long has the meeting _______?

     --- Just a minute. I will check the time.

A. begun           B. started                     C. been on                D. been begun

–How long has Mr. Liu taught English?     --- _______ 1998.     

仔细阅读对话，选择恰当的答语。

–How long has Mr. Liu taught English?     --- _______ 1998.