脉冲话机所发的脉冲信号在传输中不能保证很好的质量，因为（）A.脉冲信号在传输中易产生

修改病句。     

1．公园里的松柏、桃花等树木枝繁叶茂。 

2．校园里屹立着许多棵高大的白杨树。 

3．印刷术是我国的四大发明。 

4．小红兴冲冲地跑回家，兴高采烈地告诉妈妈自己被评为优秀学生的消息。

哪种结膜炎不常出现耳前淋巴结肿大和压痛（）

A.春季结膜炎

B.流行性角结膜炎

C.流行性结膜炎

D.衣原体性结膜炎

E.淋球菌性结膜炎

   Family quarrels and lack of free time can promote headaches in children. This is what Jennifer Gassmann and her partners have concluded in a study that appears in the current issue of the Deutsches Arzteblatt International. This study was a component of a large-scale study entitled “Children, Adolescents, and Headaches”, in which data were collected in four annual “waves” from 2003 to 2006.

Up to 30% of children around the world complain of headaches at least once a week. Out of a variety of possible factors tested in a larger study, the authors chose to look at the ones related to the children’s family and leisure time.

According to the study, boys who experience more than one family quarrel per week have a 1.8 times higher risk of developing headaches. The amount of free time available to them seems to be even more important: boys who seldom have time to themselves have a 2.1 times higher risk of developing headaches.

The behavior of parents when children complain of headaches also seems to play a major role. Both positive and negative responses from parents teach children that they can gain advantages from headaches. These responses have a particularly strong effect on the frequency of symptoms in girls, with supportive responses raising the risk of recurrent(周期性的) headaches by 25%.

The genders also differed with respect to headache frequency. Twice as many girls as boys had their symptoms at least once a week. The ages of the children, however, seemed to have no more than a minor effect on their headaches.

The study may become a reminder for parents, especially for those unpeaceful families.

68. What is the passage mainly about?

A. How family quarrels and lack of free time can promote headaches in children.

B. A new study on the frequency of headaches in children.

C. Factors which lead to children’s having headaches.

D. Advice for parents wanting to keep their children from having headaches.

69. We learn from the study that ______________.

A. most children have headaches at least once a week

B. the way a family behaves is the chief factor for the headaches of children

C. parents are to blame for the increase in headaches in children

D. girls are more likely to get headache symptoms than boys

70. Parents should learn from the passage that ______________.

A. they should spend more time with their children

B. they should avoid quarreling

C. they shouldn’t care when their children have headaches

D. they should treat boys and girls differently

休克失代偿期的微循环变化主要是（）

A.微循环收缩期

B.微循环扩张期

C.微循环衰竭期

D.直接通道开放

E.血压下降

正常足月妊娠时，羊水量约为

A．2000ml

B．500ml

C．350ml

D．1000m1

E．2500ml