Among the options provided, the correct answer is c) vinegar and oil salad dressing.
A heterogeneous mixture is one in which the components are not uniformly distributed, meaning you can often see the different parts or phases within the mixture. In the case of salad dressing made from vinegar and oil, the two liquids do not mix thoroughly. You will see distinct layers of vinegar and oil, which is a clear indication of a heterogeneous mixture.
On the other hand, options like table salt (a), air (b), steel (d), and a 14 karat gold ring (e) are considered homogeneous mixtures or solutions. In these examples, the components are evenly mixed and not easily distinguished from one another.