问题 问答题 简答题

为什么受体母畜并没有配种受孕,而将供体的胚胎移植给受体后,仍能使胚胎在受体的子宫内发育?

答案

参考答案:大多数发情的母畜,发情后不论是否配种,或配种后是否受精,在最初一段时期(周期黄体期),生殖系统均处于受精后的生理状态下,此时高水平孕酮使子宫内膜的组织增生和分泌机能增加及生理生化发生特异性变化,在生理机能上妊娠与未孕并无区别。这就给胚胎成功的移植和在受体内正常发育提供了理论依据。

阅读理解

阅读理解。

                                                                          Healthy eating

     What's the best thing to eat on a hot summer day? Many people would say ice cream. Yes, eating ice

 cream with some fruit on top is a great way to cool down. But think before you eat. If your body is hot

 from playing sports, it's not the best time to eat ice cream.

     When your body is hot, a lot of ice cream may give your stomach some problems, and you could get

 diarrhoea (腹泻). You can eat some ice cream after you've cooled down a bit and had some tea. Just try

  not to eat too much all at once!

     After dinner is another time people shouldn't eat or drink anything cold. Drink something hot after you

 eat, and your stomach will digest (消化) your food better. If you love fruit, summer is a great time for you.

  Go to the market and pick out the best fruit of the season. If you want to stay cool, oranges, bananas,

 pears and watermelons can help. Also, try to eat more ginger and gram. They will help you stay cool and

  healthy.

     In summer, bacteria (细菌) grow very fast and make your food go bad quickly. Try hard to keep

  yourself and your home clean in summer. Always eat clean, fresh food. When you feel like eating a cold

 dish, put vinegar in it to disinfect it. If you can't finish your food and want to eat it again next day, make

 sure you heat it enough to kill the bacteria in it. And when you put food in the fridge, make sure to keep

 the cooked food away from the uncooked food.

     Stay healthy this summer, and enjoy a nice treat now and then. What's inside your favourite snacks?

         

1. _____ will help you stay cool and healthy.

    A. Fruit                        

    B. Ice cream              

    C. Uncooked food          

    D. Cold tea

2. It is the best time to eat ice cream _____ .

    A. if your body is too hot from playing

    B. right after dinner

    C. after you've cooled down a bit after sports

    D. while playing football

3. From the text we can know that _____ can kill bacteria.

    A. ginger                    

    B. vinegar                  

    C. gram                        

    D. oranges

4. The text mainly tells us _____ in summer.

    A. what we can eat                                        

    B. what to eat and how to eat them

    C. how to cook food                                      

    D. how to stop food going bad

单项选择题 A1/A2型题