The acacia tree is protected from other insects by a certain species of ant. The ants, in turn, feed on a sweet secretion produced by the tree. This type of nutritional relationship is known as A) saprophytism
B) parasitism
C) commensalism
D) mutualism

some fungi obtain their nutrients from a living host (plant or animal) and are called most biotrophic fungi have fairly narrow host ranges—they are specialized on a limited called rhizomorphs that allow the fungus to grow from one tree to another. ascospores are formed inside a sac-like structure called an ascus. so your answer is a