You Have a Tube of Nutrient Broth, in Which

You have a tube of nutrient broth, in which

A) Fermentation
B) Aerobic respiration
C) Anaerobic respiration
D) Photosynthesis
E) coli is growing. Upon analyzing the broth chemistry, you ?nd:
Oxygen content has dropped a bit, but carbon dioxide has gone up a lot
Formic, acetic, and lactic acids are present
What kind of metabolism has most likely occurred?