Final answer:
Adding CuSO4 to starch with saliva results in a blue color due to the interaction of Cu2+ ions with water molecules and the light absorption properties of the copper ions.
Step-by-step explanation:
When CuSO4 (copper sulfate) is added to starch with saliva, a characteristic blue color is observed.
This occurs because the amylase enzyme present in saliva breaks down the starch into smaller units, which don't interact with CuSO4 as starch would.
However, it is the Cu2+ ions in the CuSO4 solution that are responsible for the blue coloration as they interact with water molecules and absorb light in the red region of the spectrum.
This absorption causes the solution to appear blue when white light is transmitted through it.
Therefore, the correct answer is a) Blue.