题目

An 80-year-old man was sitting on the sofa in his house along with his 45-year-old son. Suddenly a crow landed on their window. The father asked his son,“What is that?”The son replied,“That’s a crow.”After a few minutes, the father asked his son for the second time, The son said,“Father, I told you just now. It is a crow.”After a little while, the father asked his son the same question for the third time,“What is that?”This time, the son said to his father in a low and cold tone,“It’s a crow, a crow.”After a moment, the father yet again asked his son for the fourth time下列方法不能鉴别氧气和二氧化碳的是A. 滴加紫色石蕊溶液B. 观察颜色C. 滴加澄清石灰水D. 伸入带火星的木条