Final answer:
The tendency for individuals to choose mates similar to themselves is known as assortative mating.
Step-by-step explanation:
The tendency for individuals to choose mates who are like themselves is called assortative mating. Assortative mating is an individual's preference to mate with partners who are phenotypically similar to themselves, often extending to similarities in background, attitudes, and lifestyle. This form of mate selection can lead to nonrandom mating within a population, which in turn can influence the genetic structure and evolution of that population. From the options provided, the correct term for this tendency is (a) when individuals mate with those who are similar to themselves.