把下列音节补充完整。 ___óng zh___ h___ ___ìn 　l__

紊乱性房性心动过速是指P波频率>100次/分（）

A.同一份心电图上有2种或以上形态不同的P波

B.同一份心电图上有3种或以上形态不同的P波

C.心电图同一导联上有2种形态不同的P波

D.心电图同一导联上有2种或以上形态不同的P波

E.心电图同一导联上有3种或以上形态不同的P波

焊接和铆接相比，在（）方面不如铆接。

已知实数x，y满足线性约束条件  x+y-4≥0 ，目标函数z＝y－ax(a∈R)，若z取                                      2x-y-5≤0

最大值时的唯一最优解是(1,3)，则实数a的取值范围是(  )

A．(0,1)

B．(－1,0)

C．(1，＋∞)

D．(－∞，－1)

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(调查) 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（直的）. You can slouch(低头垂肩地坐)on a ball,” says Witt, “but it feels bad.” Because the students are moving, their blood (血液) increases. That carries more oxygen( 氧气) to the brain , so the kids have more energy and can pay attention longer.

“Besides, they’re fun.” says Pownall.

小题1:What will happen if a student sits on a chair all day in school? The student will_________.

A．pay more attention to his lessons

B．be fun

C．like to move around

D．sit up straighter小题2:How long has Dottie Pownall used the balls?

A．About four years.

B．Only one year.

C．In 2008.

D．Since he was a fifth-grade teacher.小题3:In how many countries are the balls used as the students’ chairs?

A．Four.

B．Three.

C．Two.

D．One.小题4:Teachers choose balls instead of chairs because sitting on balls helps the kids _________.

A．improve the students’ posture and attention

B．slouch on the chairs

C．have fun

D．Both A and C are correct answers小题5:Which is better for kids to study in class, sitting on a chair or sitting on a ball?

A．Sitting on a chair.

B．Sitting on a ball.

C．They are the same.

D．We don’t know.

会计档案保管期限从( )后第一天算起。

A．月度终了

B．季度终了

C．年度终了

D．半年度终了