Final answer:
Salt and water is the pair of substances that are most likely to form a homogeneous solution.
Step-by-step explanation:
Out of the given options, 2) Salt and water is the pair of substances that are most likely to form a homogeneous solution. A homogeneous solution is a mixture where the components are thoroughly mixed and have constant composition throughout. Salt (NaCl) dissolves easily in water (H₂O), resulting in a homogeneous saltwater solution.