问题 单项选择题

二度Ⅰ型房室传导阻滞的心电图特征是()

A.P-R间期进行性缩短,直至一个P波受阻不能下传到心室

B.相邻P-R间距进行性延长,直至一个P波受阻不能下传到心室

C.P-R间期进行性延长,直至一个P波受阻不能下传到心室

D.P-R间期>0.20秒,P波无受阻

E.P-R间期固定,P波间断受阻不能下传到心室

答案

参考答案:C

解析:二度房室传导阻滞可分为两型。Ⅰ型又称文氏现象,或称莫氏Ⅰ型,Ⅱ型又称莫氏Ⅱ型。文氏现象特点:①P-R间期逐渐延长,直至P波受阻与心室脱漏,②R-R间期逐渐缩短,直至P波受阻;③包含受阻P波的R-R间期比两个P-P间期之和为短。莫氏Ⅱ型特点:①P-R间期固定,可正常或延长。②QRS波群有间期性脱漏,阻滞程度可经常变化,可为1:1;2:1;3:1;3:2;4:3等。下传的QRS波群多呈束支传导阻滞图型

阅读理解

阅读理解。

     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.

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

2. How long has Dottie Pownall used the balls?

A. About three years.

B. Only one year.

C. In 2008.

D. Since he was a fifth-grade teacher.

3. In how many countries are the balls used as the students' chairs?

A. Four.

B. Three.

C. Two.

D. One.

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. 

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.

选择题