The Fungus Pyrenophora Tritici-Repentis Causes Disease in Wheat

The fungus Pyrenophora tritici-repentis causes disease in wheat.Only strains of P.tritici-repentis that contain the ToxA gene are able to cause disease;other strains are avirulent.The appearance of the toxin gene is recent;how does research indicate this gene was acquired?

A) It is the result of mutation in a pigment gene in the fungus.
B) It is the result of a mutation that up-regulated the expression of the previously non-expressed gene.
C) It was transferred from a pathogenic bacterium to P.tritici-repentis.
D) It was transferred from another pathogenic fungus to P.tritici-repentis.
E) It was acquired through the rearrangement of two other genes in P.tritici-repentis.