If a robin builds a nest in a big tree, the robin benefits and the tree is not or harmed. this type of symbiotic relationship is called commensalism, and it is between the and the someone i'm completely lost

tree and nest
If a robin builds a nest in a big tree, the robin benefits and the tree is not helped or harmed. This type of symbiotic relationship is called commensalism, and it is between the tree and the nest/Robin.

There are several types of biotic relationships that is occurring every single moment in the ecosystem and commensalism is one. In contrast, parasitism is the biotic relationship where one organism doesn't benefit from the other and is harmed. In this scenario with human beings and mosquitos, this phenomenon of interaction is distinguished as parasitism where mosquitos draws blood that contains nutrients from the human tissue to use it as its source of food and then leaves harmful substances and bacteria in the human’s blood stream.

The answer will be d