問題詳情

On every bottle of milk that we buy, we see the word pasteurized. It is the process invented byLouis Pasteur, to make milk free from germs and safe to drink. In 1850, life was very difficult,especially for the poor. The streets in the cities were full of garbage, and there were rats everywhere.These conditions helped diseases to spread and many people died. Louis Pasteur began studyingmicrobes. Everyone knew that meat went bad if you left it in the open air. With the help of amicroscope, you could see the microbes in the meat. But no one was sure where they came from.Old-fashioned scientists believed they were already there. Mr. Pasteur believed they were in the air.He thought: “If I boil meat juice, I’ll kill the microbes. So, if I put the juice in a bottle while it’s stillvery hot, and keep out the air, the microbes won’t get in, and the juice won’t go bad.” Mr. Pasteur hadthe answer. Louis Pasteur also wanted to kill the microbes in people. He could not boil people; he hadto find a way.
21. There are three occurrences of “they” in the paragraph. What does it refer to?
(A) diseases
(B) scientists
(C) microbes
(D) conditions

參考答案

答案：C
難度：簡單0.714286
統計：A(2),B(0),C(5),D(0),E(0)

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