单项选择题

Good morning. I am Professor Armstrong, and I am your laboratory instructor. This class is intended as a necessary part of the course, which Dr. Smith will be in charge of. This class will meet twice a week. This laboratory opens at nine. I expect you to be on time. I do not intend to wait for the latecomers or repeat what has already been covered if you miss the explanation. And do not arrive late and interrupt your neighbor. You may as well not come if you can’t be on time.
Attendance is equally important. If you miss three lab classes, you’re dropped from the labs — no excuses. You can’t complete the course without completing the lab.
Besides, safety key is here. It’s very important to keep things neat and clean, dress properly, and be Careful. You may not eat, drink or smoke in the laboratory and you should always clean the counter and wash your hands both before and after the class. Long hair must be tied back. Large clothing must not be worn. Any laboratory accident must be reported immediately.
I hope you’ll enjoy the laboratory. It’s a wonderful place, and all the requirements I’ve just mentioned are to be followed. We will begin today by learning about the microscope.
What is the main purpose of Professor Armstrong’s speech