The following pictures represent solutions of CuS,which may also contain ions other than Cu2+ and S2- which are not shown.Gray spheres represent Cu2+ ions and dotted spheres represent S2- ions. 
-If solution (1) is a saturated solution of CuS,which of solutions (2) -(4) are unsaturated?
Definitions:
Subjects
The topic or matter being discussed or described in a sentence, paragraph, or work; also individuals or entities that are being studied or observed.
Predicates
In grammar, parts of sentences that express what is said about the subject; in logic, parts of propositions that signify properties or ways of being.
Connective
A logical operator that connects two propositions in a complex statement, like "and", "or", and "if... then".
Subject
The entity being discussed or analyzed, often the focus of a sentence, theory, or experiment.
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