下图表示蛙的发育过程，正确的发育顺序是

巴斯德在实验中首先要把两个瓶内的肉汤煮沸，目的是（  ）

根据短文理解，从A、B、C、D四个选项中选择最佳答案填空。

    Alison cornered me in the kitchen. “Daddy, I really want a rat.”

    "Again?” I saw the ugly grey things with round eyes and long tails in my mind. She wanted one of those in our 1?

    “No, Daddy, a pet rat kept at home."

    This topic was around in our family for about one year. This time, Alison told 2 seriously how she would take care of the rat herself, how she would learn to be 3 by doing so. I wanted to say “no” as usual, 4 it was not the right response for this situation. I suggested that Alison should 5 me that she would be responsible by researching some basic questions we had about   6 : How much do they cost? What care do they need?

    I thought the answers she found 7 change her mind. Alison searched for information and made many notes. She learned 8the best cage for rats is and what types of food they can (and can't) eat. She learned that two rats are 9 than one — they like staying together.

    Alison proved herself with her efforts, so I 10 finally. If she continued to do so, caring for the rats and preparing food for them, she would learn the responsibility we always wanted her to have.    

    We 11 several pet stores, asking for baby rats. One store told us it just received some that would be ready on sale in a week. Alison was so 12 — her dream would come true soon.   

    On Sunday afternoon, I drove Alison there. I must say, 13 seeing the rats, I found they were much cuter. Alison 14 picked out two little ones with her soft little hands. She cradled the cage with them, 15. We went back to our car, and huge smile was still on her face.

    “I can't believe I have them after a year of begging!"

    “It wasn't your begging,” I told her. “You showed me you were responsible so I wanted to reward that.”

根据短文理解，选择正确答案。

    I'm a 20-year-old boy,and the following is my story.

    A month after I graduated from high school in August,2007,I was coming home from swim practice in the training centre of the city and was involved in a car accident.I was so seriously injured that I was in a coma for more than two months at Prince Georges Hospital.

    I suffered a lot from the experience of dying eight times during my coma and I couldn't open my mouth to talk or to communicate when I eventually came around.At that time,it seemed that walking was never going to happen again due to all the extreme injuries.Just like my body,my dreams were completely destroyed.But I was not going to let my injuries stop me from realizing my dreams.

    After receiving a total of 15 operations and 36 blood transfusions,I had to make every great effort to learn to talk,eat,walk,shower,and live on my own again.When I was out of hospital,I still had to Go to outpatient therapy in Waldorf,Maryland.After I spent a few months in a wheelchair,I took baby steps to walk on my own.It was a miracle that I was able to walk again,but I still wanted to prove that I could not only walk,but also run.When it came true,I wanted to get back into the pool again.After having a few lung tests,I was able to go in the pool a little bit each week. After a few months of swim training,I began my freshman year at St.Mary's College of Maryland and then became a proud member of the swim team.

    By telling my story,I want to make a positive influence on the world.I am just trying to live every day to the fullest and inspire other people never to give up their dreams no matter how bad a situation is to them.I remember when I was still in my hospital bed,I would have my mom and dad push me round in my wheelchair to the other rooms to see the other patients and chat with them and their family members.I wanted to let them know that everything was going to be okay.Somehow,things would work out for the best.

控制植物蒸腾作用强弱的结构是