相关需求，即某种物品的需求与其他物品相关。例如，一个汽车制造厂对引擎的需求与该厂生产

Read and answer.（阅读短文，回答问题)

     There are four seasons in a year: spring, summer, fall and winter. Each season has three months.

Spring is the first season of the year. In spring, the weather gets warmer and the trees turn green. 

Summer is the hottest season in a year. People always find cool places. They like to swim and eat

ice-creams. During the summer. the plants and flowers are at their best. Fall is a wonderful season.  

It is the time for harvest (丰收) and the peasants (农民)  are very busy. Winter is the last season

of the year. It is cold in winter. In many places it snows. Children are very happy, because they

can make a snowman and dance around it.

1. How many seasons are there in a year?

______________________________________________________________________________

2. Which one is the first season?

______________________________________________________________________________

3. Why is fall a wonderful season?

______________________________________________________________________________

4. Who are happy in winter? Why?

______________________________________________________________________________

患者，女，34岁，间歇性进食后腹胀、恶心、呕吐2年。仰卧位时加重，俯卧位、侧卧位时减轻，体检：神志清楚，体温正常，呼吸17次／分，血压90/66mmHg，脉搏72次／分，无黄疸，无贫血。两肺无啰音，心率72次／分，律齐，无杂音。腹软，腹部无包块，腹部未见胃形，腹部无压痛、无反跳痛，Murphy征阴性，麦氏点无压痛，腹部移动性浊音阴性，肝浊音界位于第4肋间，肠鸣音2次／分。既往身体健康。腹部B超、心电图、腹部立位平片、血常规、血急诊生化、血肿瘤标志均正常。胃镜见图89，上胃肠钡餐造影见图90、图91。

关于肠系膜上动脉压迫综合征的治疗的描述下列哪些是正确的？（）

A.症状轻微者应控制饮食、卧床休息

B.发病时最好采用俯卧位、侧卧位

C.恶心呕吐明显者静脉补充液体及电解质

D.症状明显时治疗上可以应用阿托品，口服或肌内注射

E.经内科治疗无效，同时合并十二指肠球部溃疡者可以进行胃次全切除、毕Ⅱ式胃空肠吻合术

F.对已形成习惯性逆蠕动者进行十二指肠血管前移术效果好

G.经内科治疗无效时可以进行十二指肠空肠侧侧吻合术，此手术方法是公认的有效术式

H.经内科治疗无效时也可以进行Treitz韧带松解术

在心肌细胞同步收缩形成正常心跳过程中，下列哪种细胞连接起重要作用？（）

A.紧密连接

B.半桥粒

C.黏着斑

D.黏着带

E.缝隙连接

细胞或生物体受刺激后所发生的一切变化称为（）。

梁桥的支座有即几种？各种支座适用于什么场合？