\textbf{Since the actual mass is always 0.75kg more than the displayed mass, they are perfectly correlated.~} 
\textbf{Suppose a certain scale is not calibrated correctly, and as a result, the mass of any object is displayed as 0.75 kilogram less than its actual mass. What is the correlation between the actual masses of a set of objects and the respective masses of the same set of objects displayed by the scale?} 

a: $$-1$$ 
b: $$-0.75$$ 
c: $$0$$ 
d: $$0.75$$ 
e: $$1$$ 