问题 单项选择题

下面有关单倍体的叙述中,不正确的是()

A.由未受精的卵细胞发育而成的个体

B.花药经过离体培养而形成的个体

C.凡是体细胞中含有奇数染色体组的个体

D.普通小麦含6个染色体组,42条染色体,它的单倍体含3个染色体组,21条染色体

答案

参考答案:C

阅读理解

阅读理解

         A group of swans(天鹅) flew down to a beach where a crow(乌鸦) was jumping around. The

crow watched them with disdain(蔑视).

        "You have no flying skills at all!" he said to the swans. "All you can do is to you’re your wings

(翅膀).  Can you turn over in the air? No, that's beyond you. Let's have a flying competition. I'll show

you what real flying is!"

         One of the swans, a strong young male(雄性) , took up the challenge. The crow flew up and

began to show his skills.  He flew in circles,  performed other flying tricks(花样), and then came down

and looked proudly at the swan.

         Now it was the swan's turn.  He flew up, and began flying over the sea.  The crow flew after him,

making all kinds of comments about his flying.   They flew on and on till they couldn't see the land  and

there was nothing but water on all  sides.  The crow was making fewer and fewer comments.   He was

now so exhausted that he found it hard to stay in the air, and had to struggle to keep himself from falling

into the water.

        The swan pretended not to notice, and said, "Why do you keep touching the water,brother? Is that

another trick?"

        "No," said the crow. He knew he had lost the competition. "I'm in trouble because of my pride! If

you don't help me, I'll lose my life. "

        The swan took pity on him, and took him on his shoulders and flew back to the beach.

1. The crow met the swan on a          .

A. beach        

B. field      

C. lake          

D. ground

2. What's the correct order of the following events?  

         a. The crow followed the swan and got into trouble.              

         b. The swan felt pity for the crow and saved it.              

         c. The crow had to ask the swan for help.              

         d. The swan accepted a challenge of performing flying tricks.

A. a, d, b, c      

B. a, b, d, c    

C. d, a, c, b      

D. d, c, a, b

3. What does the underlined word "struggle" in Paragraph 4 mean?

A.挣扎    

B.逐渐    

C.准备    

D.溺水

4. The underlined sentence means          .

A. the swan began to fly            

B. the crow began to fly            

C. it is the turn for the swan to feel proud            

D. it is the turn for the crow to feel proud

5. What do we learn from the passage?

A. Practice makes.perfect.                

B. The early bird catches the worm.            

C. No painsr no gains.                    

D. Pride goes before a fall.

填空题