题干

利用高浓度食盐溶液杀菌防腐的原理是(  )

A:由于食盐中氯有杀菌作用

B:由于高浓度食盐溶液的水分不足,以致细胞不能生存

C:由于渗透作用,使细菌细胞脱水而死亡

D:由于食盐是中性,不适于细菌生长

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答案(点此获取答案解析)

C

同类题3


—Stay a bit longer , please. It’s been such ______ fun having you here .
—Thank you , but I’ve got ______ early start tomorrow morning .

同类题4

完形填空

    One day, a professor entered the classroom and asked his students to prepare for a surprise test. They waited anxiously at their desks for the test to begin. The professor 1the question papers, with the text facing down as usual. 2 he handed them all out, he asked his students to 3 the page and begin. To everyone's surprise, there were no 4 just a black dot(点)in the center of the page. The professor, seeing the expression on everyone's face, told them the following:

    “I want you to write what you 5 there.”

    The students, 6 got started on the inexplicable(费解的)task. At the end of the class, the professor 7 all the answer papers and started reading each one of them aloud in front of all the students. All of them, with no 8, described the black dot, trying to explain its position in the middle of the sheet, etc. After all had been 9 the classroom was silent, the professor began to explain:

    “I'm not going to grade(打分)this. I 10 wanted to give you something to think about. No one wrote about the 11 part of the paper. Everyone focused on the black dot, and the same happens in our 12. We have a white paper to observe and13, but we always focus on the dark spots. Our life is a 14 given to us with love and care and we always have15to celebrate: nature renewing itself every day, our friends around us, the job that 16 our livelihood and the miracles we see every day. 17 we insist on focusing only on the dark spots: the health issues that bother us, the lack of money, the 18 relationship with colleagues, the 19 with a friend, and etc.

    The dark spots are very 20 compared to everything we have in our lives, but they are the ones that pollute our minds.”