Laboratory work is your chance to learn science first-hand. It can be fun but you must be careful to prevent injury. Listen closely when your teacher reads and explains the rules before your first lab lesson.

1.Your teacher will probably tell you the rules above        the first lab lesson.

   A. before            B. since            C. during           D. after

2.Before every experiment, you should       .

   A. taste the chemicals first

B. clean all the apparatus

   C. read all instructions carefully

D. report all the accidents to the teacher

3.When you are not sure how to use all apparatus,       .

   A. try them on your own                  B. put them back

   C. ask your teacher for help                 D. read the rules carefully

4.It is clear that you can       .

   A. bring food into the lab

B. enter the lab anytime

   C. smell chemicals as you like

D. learn science directly in the lab

5.If you get chemicals on the clothing, you can find ways to solve it in the part       .

A. Before the Experiment                 B. First Aid

C. During the Experiment                 D. After the Experiment

When the teacher ______ how to do the experiment, the bell rang.

A. explains????????????? B. will explain ????????????? C. was explaining??? ????????????? D. is explaining

Laboratory work is your chance to learn science first-hand. It can be fun but you must be careful to prevent injury. Listen closely when your teacher reads and explains the rules before your first lab lesson.

阅读理解：先阅读短文，然后根据短文内容从文后每小题的四个选项中，选出一个能完成所给句子或回答所提问题的正确答案。

　　President (总统) George W Bush is visiting an elementary school today and visits one of the 4th grade classes. They are in the middle of a discussion(讨论) of words and their meanings.

　　The teacher asks the President if he would like to lead the class in the discussion of the word“tragedy”. So the President asks the class for an example of a“tragedy”.

　　One little boy stands up and says,“If my best friend, who lives next door, is playing in the street and a car comes along and runs him over, that would be a tragedy.”

　　“No,”says Bush,“that would be an accident.”

　　A little girl puts up her hand,“If a school bus carrying 50 children drove off a cliff(悬崖), killing everyone in the bus, that would be a tragedy.”

　　“I am afraid not,”explains the President.“That is what we would call a GREAT LOSS(损失).”

　　The room goes quiet. No other children answer. President Bush looks around the mom.“Is not there someone here who can give me an example of a tragedy?”

　　At last, in the back of the room, a boy named Johnny puts up his hand. In a quiet voice he says,“If Air Force One, carrying you and Mrs Bush, was hit by a missile(导弹) and blown up to pieces, that would be a tragedy.”

　　“Right,”exclaims(大叫)Bush,“that is right, and can you tell me why that would be a tragedy?”

　　“Well,”little Johnny says,“because, as you just told us, it would not be an accident, and it sure as well would not be a great loss.”

1．President Bush tells the students ________.

[　　]

A．to welcome him

B．to give an example

C．to make a sentence

D．to ask some questions

2．Johnny is ________.

[　　]

A．in the front of the classroom

B．in the back of the classroom

C．in the middle of the room

D．on the left

3．Air Force One is ________.

[　　]

4．“Tragedy”means ________.

[　　]

5．What does the sentence“…and it sure as well would not be a great loss”mean?

[　　]

A．Of course, it's not a great loss, either.

B．It's OK that it would not be a great loss.

C．It's sure if it is not a great loss.

D．I'm sure that it would be a great loss, too.