某学生参加两门课程考试，设事件A表示第一门课考试通过，B表示第二门课考试通过，则事件“两门课至少一门没有通过”可以表示为( )。
A:
B:
C:
D:
A:
B:
C:
D:
举一反三
- 以下哪个不是波兰国旗？（） A: <img src="https://image.zhihuishu.com/zhs/onlineexam/ueditor/202007/3e56534d2a9245bd96ae3e551321035e.png"> B: <img src="https://image.zhihuishu.com/zhs/onlineexam/ueditor/202007/f5112a85457e41f5a909e00dc9d3043a.png"> C: <img src="https://image.zhihuishu.com/zhs/onlineexam/ueditor/202007/7c21067303c044f98a841c4f5f4b8d61.png"> D: <img src="https://image.zhihuishu.com/zhs/onlineexam/ueditor/202007/0ede615d89834d17bde3b47b2acbf0d6.png">
- 下列混合溶液，属于缓冲溶液的是( ) A: <img src="https://image.zhihuishu.com/zhs/onlineexam/ueditor/202007/413dde4a50bc4879b3f05933c4333509.png" /> B: <img src="https://image.zhihuishu.com/zhs/onlineexam/ueditor/202007/c18a15cd6f73457a9599b67d38591f3a.png" /> C: <img src="https://image.zhihuishu.com/zhs/onlineexam/ueditor/202007/3a623242f78047598682322d44b59454.png" /> D: <img src="https://image.zhihuishu.com/zhs/onlineexam/ueditor/202007/e85a62f542f34bcc80e9ee664fec7caa.png" />
- 下列电子分布属于激发态的是( )。 A: <img src="https://image.zhihuishu.com/zhs/onlineexam/ueditor/202007/81ae45d9bae64d52b1536457514518b5.png" /> B: <img src="https://image.zhihuishu.com/zhs/onlineexam/ueditor/202007/63d505d34b5d439f8106b60f8c554f13.png" /> C: <img src="https://image.zhihuishu.com/zhs/onlineexam/ueditor/202007/1acc5dd06db846b0b4d24bb7da1222db.png" /> D: <img src="https://image.zhihuishu.com/zhs/onlineexam/ueditor/202007/48001e23a0004fd0abda873af7d8e943.png" />
- 配制pH≈7的缓冲溶液，应选择( ) A: <img src="https://image.zhihuishu.com/zhs/onlineexam/ueditor/202007/f91db91d906d4648a281e7e2414fecf4.png" /> B: <img src="https://image.zhihuishu.com/zhs/onlineexam/ueditor/202007/d788ac460faf40348a1c3ad467417dd9.png" /> C: <img src="https://image.zhihuishu.com/zhs/onlineexam/ueditor/202007/10b2abc3968d46fd8a7e9c276d6f0b19.png" /> D: <img src="https://image.zhihuishu.com/zhs/onlineexam/ueditor/202007/cf120ba897744b3b9684f0365ded361e.png" />
- 下列离子属于9~17电子构型的是( )。 A: <img src="https://image.zhihuishu.com/zhs/onlineexam/ueditor/202007/98d5d4b38f664003989388c34b412dae.png" /> B: <img src="https://image.zhihuishu.com/zhs/onlineexam/ueditor/202007/5d447bd56a6a4e5c899da3611c5592c3.png" /> C: <img src="https://image.zhihuishu.com/zhs/onlineexam/ueditor/202007/c34f43d2aa684eac93ea994d37780085.png" /> D: <img src="https://image.zhihuishu.com/zhs/onlineexam/ueditor/202007/0048373ac18e4dbebaeb3ad4687aacb3.png" />