I like my job because it's _____. [ ]
A. hard
B. interesting
C. boring
D. busy
B
The map is _____________________.
A. white, green, blue B. white and green and blue C. white, green and blue
设U是所有属性的集合,X、Y、Z都是U的子集,且Z=U-X-Y,下列关于多值依赖的叙述中,哪个(些)是正确的 Ⅰ.若X→→Y,则X→Y Ⅱ.X→Y,则X→→Y Ⅲ.若X→→Y,且
,则X→→Y Ⅳ.若X→→Y,则X→→Z
A.只有Ⅱ
B.只有Ⅲ
C.Ⅰ和Ⅲ
D.Ⅱ和Ⅳ