Answer: Option C.
The solute solvent interaction making the beaker warm means it releases energy into the surrounding.
Explanation:
When sodium fluoride dissolves and dissociates in water, then this combo of solute and solvent will form the system. And the beaker in which both are contained is termed as the surrounding. So when the sodium fluoride dissociates in water, this means there occurs breakage in bonds of sodium flouride and as sodium fluoride is an ionic compound, so there will be breaking of ionic bonds. And ionic bonds releases more energy compared to any other kind of bond. So this release of energy from the system is given into the surrounding which inturn warms up the beaker in which the solute and solvent interacts.
Thus, the solute solvent interaction release energy into the surroundings and makes the beaker warm.
