Answer: Option (a) is the correct answer.
Step-by-step explanation:
A homogeneous mixture is defined as a mixture in which the solute particles completely or uniformly distribute into the solvent.
For example, salt in water is a homogeneous solution.
On the other hand, a heterogeneous mixture is defined as a mixture in which solute particles are non-uniformly distributed into the solvent.
For example, mud in water is a heterogeneous mixture.
In a suspension, particles of solute settle at the bottom of the solution after sometime upon coming in contact with the solvent.
For example, paint is composed of many colored particles that separate from the rest of the mixture when left in the can for a long time.
In a colloid, particles of a solute remain suspended into the solution.
For example, shaving cream is a mixture that contains small- to medium-sized particles suspended in foam.
Thus, we can conclude that out of the given options salt water contains small particles that have moved, so they are evenly spread through the mixture, is a homogeneous mixture.