Watch Carefully Please
一、(老师的特点)
1、Harry will never forget his first chemistry teacher in junior high school. 
2、He had strange ways to make his lessons lively and interesting. 
二、(准备试验)
3、Harry still remembers one of the lessons given by the teacher in the chemistry laboratory. 
4、The teacher put out three bottles filled respectively with gas, vinegar and caster oil.
三、(让学生观察)
5、Having told the students to watch, he filled a cup with the three liquids. 
6、He stirred and mixed the three together. 
四、(让学生观察后跟着做)
7、Holding up a finger, he asked the students to watch him carefully and then do exactly as he did. 
8、He dipped his finger in the mixture for a few seconds and then put a finger in his mouth. 
9、Sucking the finger, he nodded his head and smiled, looking rather pleased. 
五、(学生做的)
10、He then handed the cup to the students. 
11、Each of them dipped a finger in the mixture and sucked it. 
12、Instead of smiling, they all made faces and spat, for the mixture tasted terrible. 
六、(教导学生)
13、The teacher said to his students sadly, 
'None of you watched carefully enough to see what I did. I did suck a finger, but I did not suck the one I had dipped into the mixture.'”