The diagram below shows three families. Which set of parents has the highest fitness? A
the parents of the single child

B
the parents of two children

C
the parents of the big family

C. the parents of the big family

Explanation:

In biology, an organism that produces as much offspring is said to have a higher fitness compared to its counterpart. It is said to be biologically fit than the rest.

Therefore, in the same vein, the parents that has the biggest family is the most biologically fit of the three families.

if you listed your answers right then i believe your answer is b.