问题 单项选择题

细胞兴奋性维持是因为()

A.安静时膜对K有通透性

B.兴奋时膜对Na通透性增加

C.Na和K的易化扩散

D.膜的Na-K泵作用

E.以上都是

答案

参考答案:D

解析:膜的Na-K泵作用是细胞兴奋性维持的条件。

填空题


阅读下列函数说明和C代码,
[说明]
所谓货郎担问题,是指给定一个无向图,并已知各边的权,在这样的图中,要找一个闭合回路,使回路经过图中的每一个点,而且回路各边的权之和最小。
应用贪婪法求解该问题,程序先计算由各点构成的所有边的长度(作为边的权值),按长度大小对各边进行排序后,按贪婪准则从排序后的各边中选择组成回路的边,贪婪准则使得边的选择按各边长度从小到大选择。
函数中使用的预定义符号如下:
#define M 100
typedef struct{/*x为两端点p1、p2之间的距离,p1、p2所组成边的长度*/
float x;
int p1,p2;
}tdr;
typedef struct{/*p1、p2为和端点相联系的两个端点,n为端点的度*/
int n,p1,p2;
}tr;
typedef struct{/*给出两点坐标*/
float x,y;
}tpd;
typedef int tl[M];
int n=10;
[函数]
float distance(tpd a,tpd b);/*计算端点a、b之间的距离*/
void sortArr(tdr a[M],int m);
/*将已经计算好的距离关系表按距离大小从小到大排序形成排序表,m为边的条数*/
int isCircuit(tr r[M],int i,int j);
/*判断边(i,j)选入端点关系表r[M]后,是否形成回路,若形成回路返回0*/
void selected(tr r[M],int i,int j);/*边(i,j)选入端点关系表r*/
void course(tr r [M],tl l[M]);/*从端点关系表r中得出回路轨迹表*/
void exchange(tdr a[M],int m,int b);
/*调整表排序表,b表示是否可调,即是否有长度相同的边存在*/
void travling(tpd pd [M],int n,float dist,tl locus[M])
/*dist记录总路程*/
{
tdr dr[M];/*距离关系表*/
tr r[M];/*端点关系表*/
int i,j,k,h,m;/*h表示选入端点关系表中的边数*/
int b;/*标识是否有长度相等的边*/
k=0;
/*计算距离关系表中各边的长度*/
for(i=1;i<n; i++){
for(j=i+1;J<=n;j++){
k++;
dr[k].x= (1) ;
dr[k].pl=i;
dr[k].p2=j;
}
}
m=k;
sortArr(dr,m);/*按距离大小从小到大排序形成排序表*/
do{
b=1;
dist=0;
k=h=0:
do{
k++;
i=dr[k].p1;
j=dr[k].p2;
if((r(i].n<=1)&&(r[j].n<=1)){/*度数不能大于2*/
if (2) {
/*若边(i,j)加入r后形成回路,则不能加入*/
(3) ;
h++;
dist+=dr[k].x;
}else if (4) {
/*最后一边选入r成回路,则该边必须加入且得到解*/
selected(r,i,j);
h++:
dist+=dr[k].x;
}
}
}while((k !=n) && (h !=n));
if(h==n){/*最后一边选入构成回路,完成输出结果*/
course(r,locus);
}else(/*找不到解,调整dr,交换表中边长相同的边在表中的顺序,并将b置0*/
(5) ;
}
}while(!b);
}

阅读理解

Mules

Although the top men in smuggling(走私)business must work together, most of a syndicate’s(集团)small fry, especially the mules, know only their immediate contacts. If caught there is little they can give away. A mule probably will not even know the name of the person who gives him his instructions, nor how to get in touch with him. Usually he even does not know the person to whom he has to make delivery. He will be told just to sit tight in a certain hotel or bar until someone contacts him. In this way if he is blown, coming through airport customs he cannot unwittingly lead agents to the next link in the chain. All the persons at the receiving end do is to hang around the airport among the waiting crowd, and see that the mule comes through safely. If he does not, he is dimply written off(报废;注销)as a loss. To make identification of mules easier, several syndicates have devised their own “club ties” so that a mule wearing one can immediately be picked out.

Mules often receive careful training before embarking on their first journey. One Beirut organization, for example, uses a room with three airline seats in it. There the trainee mules sit for hours on end wearing weighted smuggling vests beneath their clothes, so that they become accustomed to standing up after a long flight in a natural way, and without revealing what they are carrying. An outfit in Brussels maintained a comfortable apartment where the mules could relax and get a firm grip on themselves on the night before their first journey; they were helped to dress before setting out for the airport in the morning. More often than not a courier will not know precisely where he is going or what flight number is until he is actually handed his tickets at the airport. This prevents the careless boast in some bar or to a girl friend the night before.

Mules occasionally run off with the goods to keep the profit themselves. As insurance against this, a syndicate often sends a high-up on the same plane to keep a wary eye on couriers, particularly new ones. Even then things can go badly wrong. One international currency smuggler who was having trouble getting money out of Britain was offered help by a group of men who said they were in a position to “fix thing” – for a fee of course. Foolishly, the smuggler agreed to accept their help. When he got to London’s Heathrow Airport, he handed over to one of the men a black suitcase containing nearly $90,000 in cash, destined for Frankfurt. Just to keep an eye on things, the smuggler went along on the same plane. When they landed at Frankfurt he was handed back his suitcase. He beat a straight path to the men’s toilet, opened the case, and found only old clothes. The courier had switched suitcase en route, but the smuggler could hardly run to the police and complain that “the man who was smuggling money out of England for me has stolen it.”

小题1:What is a “mule”?

A A person who sends smuggling goods for a syndicate is called mule.

B A person in charge of smuggling goods is called mule.

C A person who makes delivery for a syndicate is called mule.

D A person who receives instructions from a smuggler is called mule.

小题2:The sentence “if he is blown” in line (6) is closest in meaning to

A if he is arrested.                  B if he is recognized, but not necessarily arrested.

C if he is recognized and arrested.     D if he runs away.

小题3:Why does the author give an example in the last paragraph?

A To show how a smuggler is caught. 

B To show a smuggler is afraid of the police.

C To show to keep a wary eye on couriers is useless.

D To show mules may keep the profit for themselves.

小题4:how does a mule work?

A Jointly.                   B Independently.

C consciously.               D Separately.