Which one of the following is not a nitrogen-fixing organism?
| 1. | Anabaena | 2. | Nostoc |
| 3. | Azotobacter | 4. | Pseudomonas |

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The residue left after methane production from cattle dung is:
| 1. | burnt | 2. | buried in landfills |
| 3. | used as manure | 4. | used in civil construction |

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Methanogens do not produce:
| 1. | oxygen | 2. | methane |
| 3. | hydrogen sulfide | 4. | carbon dioxide |

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What would happen if oxygen availability to activated sludge flocs is reduced?
| 1. | It will slow down the rate of degradation of organic matter. |
| 2. | The center of flocs will become anoxic, which would cause the death of bacteria and eventually breakage of flocs. |
| 3. | Flocs would increase in size as anaerobic bacteria would grow around flocs. |
| 4. | Protozoa would grow in large numbers. |
During which stage of the sewage treatment are the microbes used?
| 1. | Primary | 2. | Secondary |
| 3. | Tertiary | 4. | Quaternary |

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Biogas is a mixture of:
| 1. | Methane, Carbon dioxide, and Hydrogen sulfide |
| 2. | Methane, Carbon dioxide, and Ammonia |
| 3. | Methane, Ammonia, and Hydrogen sulfide |
| 4. | Ammonia, Carbon dioxide, and Hydrogen sulfide |

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‘Toddy’, a traditional drink of some parts in southern India, is made by fermenting sap from:
| 1. | Soyabean | 2. | Bamboo shoots |
| 3. | Palms | 4. | Sugarcane |

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The ‘Roquefort cheese’ is ripened by:
| 1. | A fungus | 2. | A bacterium |
| 3. | An algae | 4. | Lichens |

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With reference to human beings, antibiotics are actually:
| 1. | Anti life | 2. | Pro-life |
| 3. | Irrelevant to life | 4. | Defining life |

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Which of the following human diseases cannot be treated by antibiotics?
| 1. | Plague | 2. | Diphtheria |
| 3. | Leprosy | 4. | Mumps |

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