The primary cause of a pearl forming is .

A. A larva that is not released after fertilization of the egg
B. Pollutants present in the water
C. The presences of a nacreous layer in oysters
D. An irritant that becomes embedded in the mantle

Which of the following is an example of competition a. the leaves of a tree prevent a small shrub from getting sunlight. three species of birds feed a different heights in the same tree. b. three species of birds feed at different heights in the same tree c. zebra and giraffe’s feed on different grassland plants d. cats living in two different homes eat the same brand of cat food.