题目内容：

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.

LABORATORY RULES
Throughout the lesson	Do not enter the science lab without the teacher's permission. No food or drinks are to be allowed in the science lab.
Before the experiment	Read all instructions carefully before every experiment. Prepare all apparatus(仪器) and arrange them so that you will not knock them over while doing the experiment.
During the experiment	If you are not sure how to use any apparatus or how to operate, ask your teacher for help. Never smell or taste chemicals unless your teacher gives permission.
After the experiment	Wash all apparatus after use and return them to the places where they were. Throw waste materials in proper waste baskets.
First aid	Report all accidents to your teacher immediately. If you spill(溅出) any chemicals onto your body or clothing, wash with plenty of water and report to your teacher.

根据材料内容选择最佳答案，并将其标号填人题前括号内。

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 the apparatus, you should ______ .

A. try them on your own

B. read the rules carefully

C. ask your teacher for help

D. put them back

4.It is clear that you can ______ .

A. bring food into the lab

B. enter the lab any time

C. smell chemicals as you like

D. learn science directly in the lab

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

A. Before the experiment B. First aid

C. During the experiment D. After the experiment