题目

关于x的一元二次方程有两个实数根，则m的取值范围是（ ）A. m≤1 B. m＜1 C. ﹣3≤m≤1 D. ﹣3＜m＜1 答案：【答案】C【解析】利用二次根式有意义的条件和判别式的意义得到，然后解不等式组即可．根据题意得，解得-3≤m≤1．故选C．A good friend of mine was complaining about her son the other day. “Did you notice,” she started, “how he didn't wait for me to get my salad before he dived into his?” True enough, the boy attacked his plate faster than a cat in the wild. Without manners, we're no more than animals. Actually, that's not true, I've been watching and feeding a group of wild cats, and they show unusual politeness toward each other .Even when food is scarce, they take turns, leaving tat least a small part for the next in line. My mother educated her three children to have good manners all the time. We were made to feel very uncomfortable as if we were sitting on pins and needles until we got used to saying please, thank you ,pardon me, and I'm sorry. And I have to say, while it was a painful learning experience, it was one of the most valuable. I can't tell you how often I sat with my friends, eating at their dinner tables, and their parents thought highly of my good manners. While it was a little embarrassing. I knew even then that my mother's teachings were paying off. Many years later, when I was attending seminars across the country, my manners were quite useful. While I regret that I haven't been a perfect example, I'm still working on it. I suppose, in this regard, my mother lives on through me, I didn't have her beautiful singing voice or her green eyes, but she did make sure I received one of her finest characteristics. 26. What did the writer's friend most probably complain about? A. Her son's eating too quickly. B. Her son's not having a healthy diet. C. Her son's not having good table manners. D. Teenagers' not having good manners. 27. The underlined word “scarce” in Paragraph 2 probably means“　　　 ”. A. too much　　　　　　　 B. not delicious C. not enough　　　　　　 D. quite hot 28. We learn that the writer's mother . A. was strict about her children's manners　 B. never punished her children C. had beautiful blue eyes　　　　　　　 D. was not good at singing 29. What does the writer think of her experience of learning good manners? A. Easy and relaxing　　 　　　B. Painful and valuable C. Easy but useless　　 　　　D. Too horrible 30. We can infer from the passage that the writer　　　 . A. is surely liked by everyone around her B. is not satisfied with most people's manners around her C. thinks she has been a perfect example to the young D. thanks her mother for teaching her the good manners a lot