Final answer:
The relationship between mistletoe and the host tree is parasitic, as the mistletoe benefits at the expense of the tree.
Step-by-step explanation:
The relationship between a mistletoe plant and the tree that it grows in can generally be described as parasitism. This is because mistletoe is a parasitic plant that attaches to the host tree, extracting water and nutrients from it. While the mistletoe benefits from this relationship, the host tree is typically harmed, as it loses vital resources. Therefore, the correct answer to the given question is B) Parasitism. On the other hand, mutualism is characterized by both species benefiting from the interaction, and commensalism describes a relationship where one species benefits while the other is not significantly affected. Competition is when two species or individuals compete for the same resources, which is not the case with mistletoe and its host tree.