A free-living nitrogen-fixing cyanobacterium that can also form a symbiotic association with the water fern Azolla is:

1. Chlorella

2. Nostoc

3. Anabaena

4. Tolypothrix

Common indicator organism of water pollution is:

1. Eichhornia crassipes

2. Escherichia coli

3. Entamoeba histolytica

4. Lemna pancicostata 

Azolla is used in the cultivation of:

Which one produces gas by decomposing the gobar (Dung) in gobar gas:
1.  Fungus
2.  Virus
3.  Methanogenic bacteria
4.  Algae

Which bacteria is utilized in a Gobar gas plant:

1. Methanogens

2. Nitrifying bacteria

3. Ammonifying bacteria

4. Denitrifying bacteria

During the formation of bread it becomes porous due to the release of CO₂ by the action of:

Which of the following is used to manufacture ethanol from starch:

1. Penicillin

2. Saccharomyces

3. Azotobactor

4. Lactobacillus

Escherichia coli is used as an indicator organism to determine the pollution of water with:

1. Heavy metals

2. Faecal matter

3. Industrial effluents

4. Pollen of aquatic plants

During anaerobic digestion of organic waste, such as in producing biogas, which one of the following is left undegraded:

1. Lipids

2. Lignin

3. Hemi-cellulose

4. Cellulose

Which of the following plants are used as green manure in crop fields and in sandy soils:

1. Crotalaria juncea and Alhagi camelorum

2. Calotropis procera and Phyllanthus niruri

3. Saccharum munja and Lantana camara

4. Dichanthium annulatum and Azolla nilotica