The correct option is C A - resource partitioning, B - MacArthur
When more than one species compete for the same resource in nature, they might evolve mechanisms to promote co-existence.
MacArthur studied five closely related species of insectivorous birds called warblers. They lived on the same coniferous trees. He observed that the different species of warbler divided their time differently in various parts of the tree. One species of bird was found to feed at the tips of branches while a different species fed mostly in the middle zone of the tree. A third warbler species fed at the base of tree. Similarly, various different positions on trees were distinguished.
MacArthur also recorded details of the warblers' foraging habits and discovered that they differed too. They also had different sleeping times, and thus the times of their peak food requirements were not the same. Thus, they were able to co-exist by reducing the intensity of competition for the same resource i.e supply of insects. This phenomenon is called resource partitioning.
Competitive exclusion principle was proposed by Georgy Gause, a Russian biologist. It states that two closely related species competing for the same resources cannot coexist indefinitely and the competitively inferior one will be eliminated eventually. For example, the Abingdon tortoise in Galapagos Islands became extinct due to the presence of goats on the island who had a better grazing ability than the tortoises.