问题 选择题

下列关于细菌的叙述中,正确的是(  )

A.绝大多数细菌对人类是有害的,少数细菌对人类有益

B.细菌细胞里也有染色体

C.每个细菌都是独立生活的

D.一个细菌也是一个细胞,所以也有完整的细胞壁、细胞膜、细胞质和细胞核

答案

A、细菌、真菌等微生物的种类多种多样,大多数细菌、真菌等微生物对人类是有益的,如微生物的发酵在食品的制作中有重要的意义.少数微生物对人类是有害的,有些微生物能使人或其他生物患病.

B、能繁殖下一代的,不一定都有染色体.染色体是由蛋白质和DNA构成,其主要成分是DNA.染色体是有空间结构的,而DNA是没有空间结构的.染色体只存在于真核生物的 细胞中,这里所谓的真核生物是指:除原核生物,病毒外的生物.细菌正是原核生物的一种,是没有染色体的,但这不代表细菌没有DNA,细菌的遗传物质是DNA,但存在于细菌中的DNA是裸露的,是不含蛋白质的,在生物学上,把细菌中具有遗传效应的DAN称为拟核(即不是真的核).因此,说细菌有染色体是不正确的.

C、细菌都是单细胞的,能独立生活,体内都没有叶绿体,不能进行光合作用,所以只能利用现成的有机物生活,营养方式是异养,大多是腐生或寄生,都进行分裂生殖.据此可知,虽然有些细菌相互连接成团或长链,但每个细菌都是独立生活的.

D、细菌属于单细胞生物,一个细菌就是一个细胞,细菌的基本结构包括:细胞壁、细胞膜、细胞质、未成形的细胞核;

故选:C

阅读理解

Modern life is impossible without traveling. The fastest way of traveling is by plane. With a modern airline you can travel in one day to places which it took a month or more to get to a hundred years ago.

Traveling by train is slower than plane, but it has its advantages. You can see the country when you are traveling through. Modern trains have comfortable seats and dining cars. They make even longer journey enjoyable.

Some people prefer to travel by sea when possible. There are large liners and river boats. You can visit many other countries and different places. And traveling by sea is a very pleasant way to spend a holiday.

Many people love to travel by car. You can make your own timetable. You can travel three or four hundred miles or only fifty or one hundred miles a day, just as you like,You can stop wherever you wish where there is something to see, at a good restaurant where you can enjoy a good meal, or at a hotel to spend the night. That’s why travelling by car is popular fpr pleasant trips,while people usually take a train or plane when they are travelling on business.

小题1: From the passage we know the fastest way of travelling is _______.

A. by train     B, by sea      C. by plane

小题2:The underlined word “they” in the 2nd paragraph refers to _____.

modern trains in the country

comfortable seats and dining cars

the travellers on the modern trains

小题3: If we travel by car, we can__________.

make the longer journey enjoyable

travel to a very far place in several minutes

make our own timetable

小题4:When people travel on business , they usually take ______.

a plane or a car

a train or a plane

a boat or a train

小题5:How many ways of travelling are mentioned in the passage ?

A.  Four      B. Three      C. Two

解答题