HW 11-117

[Ning_Yao_1B]

Can anyone explain what does the solution manual mean for 11-117 (f)?
"Because water is a liquid, it is by definition present at unit concentration, so changing the amount of water will not affect the reaction. As long as the glucose solution is dilute, its concentration can be considered unchanged. "
What does unit concentration mean? and what does the second part mean? does it mean that the concentration of glucose solution will be unchanged by adding water?

[Hao 1I]

Because the glucose solution is considered very dilute, the change in solvent concentration due to water would be so insignificant that it can be ignored.