The Biology in the News Features States That "Fecal Transplant

The Biology in the News features states that "fecal transplant experiments have established cause and effect" between the gut microbiome and weight gain.To do this,they showed that

A) weight gain results in a shift in the gut microbiome makeup.
B) certain combinations of bacteria in the gut microbiome lead to weight gain.
C) fecal transplants had no effect on the health of the subject.
D) decreasing the number of bacteria present in the gut caused a loss in weight of the subject.