21. The acetate-utilizing methanogens are responsible for

A. 20% of methane produced in a biogas reactor
B. 50% of methane produced in a biogas reactor
C. 70% of methane produced in a biogas reactor
D. 85% of methane produced in a biogas reactor

22. Which of the following is responsible for the corrosion problem?

A. Iron bacteria
B. Sulfur bacteria
C. Slime forming bacteria
D. All of these

23. Water testing relies on the detection of certain indicator organisms known as

A. acid-fast bacteria
B. bacteroids
C. coliforms
D. dinoflagellates

24. The death of a river by environmental pollutants ultimately results from

A. the overpopulation of algae
B. the overabundance of toxic proteins
C. the depletion of oxygen
D. the buildup of sediment on the river bottom