Paul (1) ________ forgets his first teacher of chemistry. The teacher was a short man with a pair of thick glasses. He always made his lessons (2) ________ and (3) __________. One day in a chemistry experiment in the lab, he made a mixture (4) ________ filling a cup (5) ________ some petrol, castor oil and vinegar. The students felt very interested and listened (6) __________. The little man then said to the students, “Now, watch me (7) ________.” He dipped one finger into the cup (8) __________a few seconds, took it (9) ________ and put his finger (10) ________ his mouth. He looked (11) ________ pleased and said with a smile, “It tastes (12) ________!” He then asked the students to do just what he had done. He handed the cup (13) ________ the class. Each student tried to do as the teacher did. Instead of smiling, each of them made a face. The mixture tasted (14) ________!