Answer:
Soluble - salt
Insoluble - sand and stapler pins
Step-by-step explanation:
The salt is soluble because it is an ionic solid which ready dissolves in water to form a solution.
The sand is insoluble because, it is a non-metallic solid which does not readily dissolve in water while, the stapler pin is insoluble because it is a metallic solid which does not readily dissolve in water.