Robins typically lay four eggs. Four eggs allow the offspring to be well fed, whereas larger clutches may result in malnourished chicks that have a lower chance of survival. Fewer than four eggs per clutch may result in no surviving offspring if the eggs are preyed upon. Which pattern of natural selection most likely acts to keep four eggs the most common clutch size

Stabilizing selection

Explanation:

The process of natural selection selects a species in one of the three ways: stabilizing selection, directional selection and disruptive selection.

During the process of stabilizing selection, nature does not favour the extreme phenotypes of the population but the intermediate phenotype with the maximum number of population.

In the given question, the Robin laid four eggs, neither more than four nor less than four which could have more disadvantages than the advantages.  Since the intermediate number of eggs is favoured by nature therefore the stabilizing pattern is observed.

Thus, Stabilizing selection is correct.