36. Which of the following is the suitable temperature range for mesophiles?

A. 20-30°C
B. 25-40°C
C. >40°C
D. None of these

37. The exponential phase of growth curve of bacteria is of limited duration because of

A. rise in cell density
B. accumulation of toxic metabolites
C. exhaustion of nutrients
D. all of these

38. A culture broth tube was very turbid at the bottom of the tube but clear at the top of the tube indicating that the

A. broth is sterile
B. organism can tolerate oxygen
C. organism cannot produce superoxide dismutase and/or catalase
D. organism should be grown in an anaerobic chamber

39. In the exponential phase, the cells and cell mass

A. first increases then decrease
B. decreases
C. are constant
D. double at a constant rate

40. What is the primary source of food for marine life?

A. Phytoplankton
B. Zooplankton
C. Seaweed
D. Grass