Unlike Most Other Eukaryotes, Microsporidia Do Not Have Mitochondria

Unlike most other eukaryotes, microsporidia do not have mitochondria. However, their genome contains genes that are related to mitochondrial function. This suggests that

A) mitochondrial-function genes have been transferred by viral transmission from other fungal species.
B) microsporidia used to have mitochondria but they have been lost.
C) at some stage in the past, microsporidia have fused with another fungal phyla and produced a hybrid that still carries some of the mitochondrial-function genes even though they are now non-functional.
D) microsporidia no longer produce asexually.
E) microsporidia energy requirements are not ATP driven.