问题
选择题
The football game is not interesting. It's very ______. [ ]
A. difficult
B. interesting
C. relaxing
D. boring
答案
答案：D
搜题请搜索小程序“爱下问搜题”
The football game is not interesting. It's very ______. [ ]
A. difficult
B. interesting
C. relaxing
D. boring
答案：D
，若X→→Y在R(W)上成立，则X→→Y在R(U)上成立
，则X→→Y'在R(U)上成立