Before the introduction of the yellow crazy ant to Christmas Island, land crabs ate many plant seedlings in the forest, maintaining a relatively clear forest floor. As the crab population has declined, plant seedlings have flourished. The forest floor is now covered with plants. Choose the statement that best describes what is occurring on the forest floor.

A. Primary succession is occurring because the ant is a new species changing the ecosystem.
B. Secondary succession is occurring because the organisms on the forest floor are changing.
C. Climax vegetation is occurring because the seedlings finally have the chance to grow.
D. Primary succession is occurring because more plant life is healthier for the ecosystem.