Which of These Things Does Our Gut Microbiome NOT Do

Which of these things does our gut microbiome NOT do:

A) produce certain compounds on which our bodies depend, including some of the enzymes that help us break down food
B) keep the gut's lining healthy and fight off certain pathogens
C) regulate appetite and immune function
D) actually the microbiome does ALL these things
E) influence mood as well as affecting food choices