In humans, babies that are born too small often lack the reserves to thrive, and babies that are too large are prone to difficult births.

Since babies at the extremes are less likely to survive, evolutionary pressures favor moderately-sized babies.

What type of selection is this an example of?

A. Artificial Selection
B. Directional Selection
C. Stabilizing Selection
D. Disruptive Selection

Explanation:

Stabilizing selection is a type of natural selection which favors intermediate genotype but eliminate extreme genotypes (inferior and superior)

Stabilizing selection is not a common phenomenon in the history of evolution of earth, so it is not a main reason of species diversity on earth

In the given example of humans, babies that are born too small lack the reserve to thrive (inferior genotype) and babies that are too large are prone to difficult births (superior genotype) whereas moderately-sized babies are favored (intermediate genotype) so this clearly reflects stabilizing selection

the denominator has a very specific role.