问题 单项选择题

心室的易损期在下列哪个时间内()

A.QRS波末到ST段开始后20ms

B.T波升至顶峰之前约30ms

C.P波初始20ms

D.P-R间期内

E.P波初始10ms

答案

参考答案:B

解析:心房的易损期位于QRS波末到ST段开始后20ms,心室的易损期位于T波升至达到顶峰之前约30ms临床上采取电击复律术治疗心律失常时,常用心电图R波触发并经一定时间延迟输出直流同步电击,使刺激不致落入心室的易损期内,以免引起心室颤动。

选择题
阅读理解

阅读理解。

      Charlie studied in a famous college for four years. He studied hard and did well in all his subjects. He

hoped to become a good teacher. This year he left the college and began to work in a middle school. He likes

his students and is strict (严格的) with them. He does his best to make his classes lively and interesting. 

      One day he carefully explained a chemical reaction (反应) to the students of Grade 2 in the chemistry

lab. 

      "Be careful, everyone," he said loudly. "Before I make the experiment, there're twenty five atoms of

carbon (碳原子), but after I finish it, there're twenty four atoms of carbon left!" He stopped to watch the

classroom and hoped his students would go on explaining it. But the young men looked at each other and

nobody answered him. He had to ask, "What happens? What makes the atom lost?"

      The classroom was very quiet and none of the students looked at their teacher. "Who can tell us where

it has gone?" Suddenly a soft voice came from the back row, "We did not see anybody leave the lab!"

1. Charlie began to work in the middle school because _____.[ ]

A. he had been in the school for four years

B. he couldn't do anything except teaching

C. he hoped to become a good teacher

D. he did well in all his subjects

2. Charlie hopes _____, so he does his best to make his classes lively and interesting. [ ]

A. all his students could understand him

B. his students wouldn't be afraid of him

C. his students carefully watched him making the experiment

D. his students could do well in chemistry

3. That day Charlie wished _____. [ ]

A. his students could learn the chemical reaction

B. his students could find the atom of carbon

C. his students could count (数) the atoms of carbon

D. his students could make the experiment

4. The students couldn't answer Charlie's questions because _____. [ ]

A. none of them had seen the atoms

B. they didn't understand their teacher

C. the chemical reaction was too complicated

D. they all wanted to drop the subject

5. In fact, _____. [ ]

A. Charlie failed that day

B. the student in the back row didn't watch her teacher carefully

C. the student in the back row hadn't learned chemistry before

D. Charlie failed in making the experiment