问题
选择题
| 下面给出3个论断： ①{0}是空集； ②若a∈N，则-a∉N； ③集合B={x∈Q|
其中正确的个数为（ ）
|
答案
①{0}不是空集，集合中有元素0，故①不正确；
②若a∈N，则-a∉N，a=0时，不正确，故②不正确；
③∵x∈Q，∴集合B={x∈Q|
∈N}是无限集，故③不正确．6 x
故选A．
搜题请搜索小程序“爱下问搜题”
| 下面给出3个论断： ①{0}是空集； ②若a∈N，则-a∉N； ③集合B={x∈Q|
其中正确的个数为（ ）
|
①{0}不是空集，集合中有元素0，故①不正确；
②若a∈N，则-a∉N，a=0时，不正确，故②不正确；
③∵x∈Q，∴集合B={x∈Q|
∈N}是无限集，故③不正确．6 x
故选A．
I have a good friend. Her name is Kate. She is American girl. She is eleven. She with her family in China. There are people in her family. They’re her father, her mother, her brother and herself(她自己). She has a cat. name is Mimi. It’s Sunday today. They at home. Look! Kate with Mimi. Her father is reading newspapers. Her mother is cleaning the house. Where is her brother Jim? He is doing homework in his study. Kate Chinese very much, but she can’t it very well. Jim likes soccer. He can play it very well.
|