Asmall crystal of the slightly soluble salt, caso4, dissolves in a solution of calcium sulfate. the original solution must have been:
dilute and saturated
dilute and unsaturated
concentrated and saturated
concentrated and unsaturated

dilute and unsaturated

Explanation:

A dilute solution has a low concentration of solute in solvent. A concentrated solution has a high concentration of solute in solvent. In an unsaturated solution more solute can be dissolved in the solvent to form a solution. In a saturated solution more solute cannot be dissolved in the solvent to form a solution.

Since more CaSO₄ can be dissolved in CaSO₄ solution the solution is both dilute and unsaturated.  

they are made of gases.

they have a spherical shape.

they make energy through fusion.