Astudent mixes a spoonful of sugar into a glass of water and stirs until the sugar dissolves completely. match each substance to its role in the dissolving process.

I believe you are referring to the solvent and solutes in the question... remember, the solvent is what the substance is being dissolved in.  the solute is what is being dissolved.  So, water here acts as a solvent, while sugar is the solute :)

a saline water is fed to a reverse osmosis unit at flow rate o rotameter connected to reject (retentate) line reads 8 installed in reject and permeate line reads 15.2 milli siemens/cm and 300 micro siemens/com respectively.