Write a multi-choice question for the following article: Article: 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 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 and Japan," says Witt, " Research shows that sitting on the balls makes them sit up straighter . You can slouch on a ball," says Witt, "but it feels bad." Because the students are moving, their blood increases. That carries more oxygen( ) to the brain , so the kids have more energy and can pay attention longer. "Besides, they're fun." says Pownall.
Question: Teachers choose balls instead of chairs because sitting on balls helps the kids _ .Options:A improve the students' posture and attentionB slouch on the chairsC have funD Both A and C are correct answersAnswer:D