In symbiotic relationships, groups of two or more organisms live in physical proximity. The types of symbiosis that depicts commensalism is

Commensalism refers to relationship wherein one organism is benefitted while other remains unaffected. Mutualism is association of organisms wherein both are benefitted. Ergets are small birds that sit on back of cow and mostly feed on grasshoppers that are stirred when herd move through field/cropland. Ergets derive nutritional benefit from this association while cow remain unaffected, making it an example of commensalism. Other examples represent mutualism wherein both partners are benefitted. Thus, the correct answer is option A.