问题 选择题

根尖之所以具有分裂能力,是因为根尖具有(  )

A.根冠

B.分生区

C.伸长区

D.成熟区

答案

答案:B

题目分析:A、根冠位于根的顶端,属于保护组织,细胞比较大,排列不够整齐,像一顶帽子似地套在外面,具有保护作用,A错误;

B、分生区被根冠包围着,属于分生组织,细胞很小,细胞壁薄,细胞核大,细胞质浓,具有很强的分裂能力,能够不断分裂产生新细胞,向下补充根冠,向上转化为伸长区,B正确;

C、伸长区在分生区上部,细胞逐渐停止分裂,开始迅速伸长,是根伸长最快的地方,是根深入土层的主要推动力,能够吸收水分和无机盐,C错误;

D、成熟区也叫根毛区;在伸长区的上部,细胞停止伸长,并且开始分化,表皮一部分向外突起形成根毛.根吸收水分和无机盐的主要部位.成熟区及其上部,根内部一部分细胞分化形成导管,能输导水分和无机盐,D错误.

故选:B.

阅读理解

A blocked airway(呼吸道) can kill someone in three to four minutes, but it can take more than eight minutes for an ambulance to arrive. So a simple procedure such as opening someone's airway can save their life while they're waiting for emergency medical help. This means you're more likely to give first aid to someone you know than a stranger.

There are many misconceptions(误解) surrounding first aid. Below are the ‘most popular’ ones with details of what you should do.

You should put butter or cream on a burn. The only thing you should put on a burn is cold water - keep the butter for cooking. Put the affected area under cold running water for at least ten minutes.

The best way to treat bleeding is to put the wound under a tap. If you put a bleeding wound under a tap you wash away the body's clotting agents(凝血剂) and make it bleed more. Instead put pressure on the wound with whatever is available to stop or slow down the flow of blood. As soon as possible call 999. Keep pressure on the wound until help arrives.

Nosebleeds are best treated by putting the head back. If you put the head back during a nosebleed, all the blood goes down the back of the airway. Instead advise them to tilt(倾斜) their head forwards and ask the person to pinch(捏) the end of their nose and breathe through their mouth.

You need lots of training to do first aid. You don’t - what you mostly need is common sense. You can learn enough first aid in a few minutes to save someone's life – whether it’s from a book, attending a course or watching videos online.

Remember: anyone can save a life

小题1:The most important point to save a person’s life is to ensure _____.

A.his smooth breath

B.ambulances’ arriving time

C.the quiet surroundings

D.emergency medical help小题2:If a person is burnt, what you should do immediately is to _____.

A.put some cream on the burn area

B.cook some butter for the burn

C.place the burn under cold running water

D.wash the affected area for a long time小题3:If a bleeding wound is put under a tap, what should happen?

A.It will help the bleeding stop at once.

B.It will help produce more clotting agents.

C.It will produce more pressure on the wound

D.It will bleed more and hard to stop小题4:Which of the following statement is RIGHT?

A.When a person’s nose bleed, please put the head back.

B.You can learn first aid in quickly in different ways.

C.When a person is burnt, crap the burn until help arrives.

D.Not everyone can do first aid to save a life.小题5:The passage mainly tells us _____.

A.how to learn first aid by yourself

B.some misunderstanding about first aid

C.the importance of first aid

D.how to help medical team save a life

单项选择题