Most swiss starlings produce four to five eggs in each clutch. those producing fewer or more than this have
reduced fitness. which of the following terms best describes this?
a) artificial selection
b) directional selection
c) stabilizing selection
d) disruptive selection
e) sexual selection

Ans. (C). stabilizing selection.

Stabilizing selection is defined as a variant of natural selection that stabilizes a particular trait in a population on an average trait value (non-extreme trait value). It favors individuals with intermediate variants, instead of individuals having extreme traits.

The females, which lay 4-5 eggs in each clutch, are showing an average or intermediate trait, while the females, which produce fewer or more eggs than this are showing extreme traits. Hence, individuals with extreme traits will show reduced fitness due to stabilizing selection.  

Thus, the correct answer is option (C).

i am going to guess that it is co2.