Answer: A) See which cup feels heavier.
Explanation:
Density is defined as the mass contained per unit volume.

Thus if a liquid is more denser than water, it contains more mass per unit volume and thus feel heavier.
We cannot taste or touch liquids as the liquid can be corrosive.
Both the liquids can be polar and thus both can dissolve ionic compound i.e salt in it.
Thus the other liquid that has greater density than water feels heavier than water.