问题 单项选择题

假定一个链队列的队首和队尾指针分别为front和rear,则判断队空的条件为( )。

A.front==rear

B.front!=NULL

C.rear!=NULL

D.front==NULL

答案

参考答案:D

解析:[分析] 链队列是用链表的方法来表示的队列,对链队列的插入删除操作只需要修改头指针或尾指针,当删除头指针时,若队列中还有其他元素,则头指针指向其直接后继,若删除非头指针,否则头指针保持不变,也就是说只要队列不空,头指针始终指向一个元素。

阅读理解

阅读理解。

     Like most people, you've probably never given your blood glucose (糖) a second thought, unless you have

diabetes (糖尿病). But researchers now know that whether or not you have diabetes, eating too much can

make your blood glucose go up and down and can increase the danger of heart disease. It may be even bad for

your memory.

     This realization has greatly changed the way we understand food and health. Luckily, none of these things

happen ovemight, and even small changes in the food you eat every day can start you on a healthier path.

     When you are hungry, do you reach for a chocolate cake or a box of biscuits? These "fast-acting" foods

are handy and they take no time at all to dissolve (溶化) in your stomach. Then they race into your blood,

running through your body with blood glucose. The trouble is the comfort doesn't last long, leaving you feeling

hungry again. As a result, your blood glucose will run out of control.

     It's no wonder most of us have less energy than we'd like and feel tired too often. It's also no wonder that

most of us weigh more than we want to. Yes, eating too much and exercising too liLtle are main reasons, and

ever changing blood glucose will send you shopping for bigger jeans.

     For most of us even when our blood glucose goes up and down after a large meal, our body can bring it

back to normal in a few hours. Only people with untreated diabetes have blood glucose levels that stay quite

high most of the time.

     For a long time, doctors thought that only these people needed to take care of their blood glucose levels.

Now, we know that even in healthy people, high levels after meals can damage (损坏) the body, even if it

never causes diabetes.

1. How does our blood glucose change after a large meal?

A. It remains unchanged.

B. It stays on high levels.

C. It goes up and down.

D. It comes back to normal.

2. What does the writer think of "fast-acting" foods?

A. He thinks they are delicious.

B. He thinks they are easy to get.

C. He thinks they make us healthy.

D. He thinks they damage our body. 

3. What shall we do if we want to keep the normal blood glucose?

A. Check our blood glucose after each meal.

B. Have proper food and exercise every day.

C. Eat certain kind of medicine before meals.

D. Ask the doctor for help from time to time.

单项选择题