完形填空Mrs.Green has worked in the school for many years.The st

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Mrs.Green has worked in the school for many years.The students all 1 her.She is a teacher of chemistry.She 2 chemistry from the lowest to the highest grades in the school.Sometimes the lower grades learn quickly ,but sometimes they are very 3 ,and then Mrs.Green has to repeat things many times.This year,the first grade students have been studying chemistry for a few weeks.One day Mrs.Green asked the students ,"What is water?4 knows?There was a silence for a few seconds and Mrs.Green felt 5 .Just then one student raised his 6 ."Yes,Dick?" said Mrs.Green encouragingly.He is not one of the 7 children in the class.so she was 8 that he could answer."Water is a liquid which has no 9 until you wash your hands in it," the boy 10 with great confidence.