Which of the following is an example of commensalism?

All of the above

The correct answer is Option (4) - All of the above.

Commensalism: This is the interaction in which one species benefits and the other is neither harmed nor benefited. An orchid growing as an epiphyte on a mango branch, and barnacles growing on the back of a whale benefit while neither the mango tree nor the whale derives any apparent benefit. The cattle egret and grazing cattle in close association, a sight you are most likely to catch if you live in farmed rural areas, is a classic example of commensalism.

The example of an orchid growing as an epiphyte on a mango branch represents commensalism because the orchid benefits by using the tree as support and accessing sunlight, while the mango tree is not affected.

Barnacles growing on the back of a whale is another example of commensalism. The barnacles benefit by having a stable substrate to attach to and access to food particles in the water, while the whale is not significantly affected.

The association between cattle egrets and grazing cattle is also an example of commensalism. The egrets benefit by foraging near the cattle and feeding on insects stirred up by their movement, while the cattle are not impacted by the presence of the egrets.

In all these cases, one species benefits while the other is not harmed nor benefited, illustrating the concept of commensalism.