(c) Damaged seeds would float on top of water.
Damaged seeds are hollow from inside. That means their inner content is either dried up due to harsh environmental conditions or is eaten up by the microbes. So the inner content becomes hollow and thus it gets lighter.
As we know that lighter particles float on water because of their low density hence damaged seeds float on water while the good seeds which have their full inner content settles at the bottom of the container in which water is present.