Tinbergen Experimented with Nesting Birds and Found That Their Laborious

Tinbergen experimented with nesting birds and found that their laborious efforts in removing broken eggshells from their nests functioned to __________.

A) make the nest less attractive to predators that might prey on their young chicks
B) keep the nest free of germs and disease that might fester on the broken shells
C) protect the young chicks from injury on the sharp edges of the broken shells
D) make the nest more comfortable for the parents to perch on for prolonged periods of time