搜题请搜索小程序“爱下问搜题”
问题 选择题

一同学从草履虫培养液中取草履虫时，将吸管伸进了培养液的底层，结果发现培养液中没有草履虫；另一位同学则在培养液的表层吸取培养液并发现了许多草履虫，这是因为（　　）

A．培养液表层含营养物质多

B．培养液表层含氧多，草履虫的生活需要氧气

C．培养液表层含营养物质少

D．培养液表层含氧少，草履虫的生活不需要氧气

答案

答案：B

名词解释

纤维素
查看答案
单项选择题 案例分析题

Most people have no idea of the hard work and worry that gointothe collecting of those fascinating birds and animals that they pay to see in the zoo.One of the questions that is always asked of me is 1 I became an animal collector in the first 2.The answer is that I have always been interested in animals and zoos.According to my parents, the first word I was able to say with any 3 was not the conventional “mamma” or “daddy”,4 the word “zoo”, which I would 5 over and over again with a shrill 6 until someone, ingroupsto 7 me up, would take me to the zoo.When I 8 a little older, we lived in Greece and I had a great 9 of pets, ranging from owls to seahorses, and I spent all my spare time 10 the countryside in search of fresh specimens to 11 to my collection of pets.12 on I went for a year to the City Zoo, as a student 13 , to get experience of the large animals, such as lions, bears, bison and ostriches,14 were not easy to keep at home.When I left, I 15 had enough money of my own to be able to 16 my first trip and I have been going 17 ever since then.Though a collector's job is not an easy one and is full of 18 ,it is certainly a job which will appeal 19 all those who love animals and 20.

请在19处填上正确答案（）

A.for

B.with

C.to

D.from
查看答案