51. Due to which of the following organisms, yield of rice has been increased ?

A Anabaena
B Bacillus popilliae
C Sesbania
D Bacillus polymexa
Answer :   Anabaena
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52. A nonphotosynthetic aerobic nitrogen fixing soil bacterium is

A Rhizobium
B Clostridium
C Azotobacter
D Klebsiella
Answer :   Azotobacter
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53. Which one of the following pairs is not correctly matched?

A Streptomyces - Antibiotic
B Serratia - Drug addiction
C Spirulina - Single cell protein
D Rhizobium - Biofertilizer
Answer :   Serratia - Drug addiction
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54. In gobar gas, the maximum amount is that of

A butane
B methane
C propane
D carbon dioxide
Answer :   methane
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55. Select the correct statement from the following?

A Biogas is produced by the activity of aerobic bacteria on animal waste
B Methanobacterium is an aerobic bacterium found in rumen of cattle
C Biogas, commonly called gobar gas, is pure methane
D Activated sludge-sediment in settlement tanks of sewage treatment plant is a rich source of aerobic bacteria
Answer :   Activated sludge-sediment in settlement tanks of sewage treatment plant is a rich source of aerobic bacteria
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56. Which of the following is put into Anaerobic sludge digester for further sewage treatment?

A Floating debris
B Effluents of primary treatment
C Activated sludge
D Primary sludge
Answer :   Activated sludge
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57. Which one of the following help in absorption of phosphorus from soil by plants?

A Glomus
B Rhizobium
C Frankia
D Anabaena
Answer :   Glomus
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58. Which one of the following pairs is wrongly matched ?

A Yeast - ethanol
B Streptomycetes - antibiotic
C Coliforms - vinegar
D Methanogens - gobar gas
Answer :   Coliforms - vinegar
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59. A good producer of citric acid is:

A Pseudomonas
B Clostridium
C Saccharomyces
D Aspergillus
Answer :   Aspergillus
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60. Which of the following in sewage treatment removes suspended solids?

A Secondary treatment
B Primary treatment
C Sludge treatment
D Tertiary treatment
Answer :   Primary treatment
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