设U为所有属性，X，Y，Z为属性集，Z＝U-X-Y。若X→→Y，且Z＝，则称X→→Y为（）的多值依赖。
参考答案：平凡
Which statement concerning Montauk Point Light is TRUE?（）
A.The light comes on at sunset
B.There is an emergency light if the main light is extinguished
C.The height of the light is 24 feet
D.The tower is painted with black and white stripes
单色胶印机印刷多色时为（）叠印。
