sentence2_structure: A(n) beneficial relationship<>exists<>when a certain type of tree's roots need a fungus present in order$$$a certain type of tree's roots<>need<>a fungus present in order
sentence1: The third major group of fungi is again associated with certain trees, but rather than harming the trees, they are often beneficial forming an intimate relationship with the tree's root system.
sentence2: A(n) beneficial relationship exists when a certain type of tree’s roots need a fungus present in order to grow normally.
question: Which type of relationship exists when a certain type of tree’s roots need a fungus present in order to grow normally?