Which one of the following microbes forms a symbiotic association with plants and helps them in their nutrition?

1. Azotobacter

2. Aspergillus

3. Glomus

4. Trichoderma

A nitrogen-fixing microbe associated with Azolla in rice fields is:

1. Spirulina

2. Anabaena

3. Frankia

4. Tolypothrix

The common nitrogen-fixer in paddy fields is:

1. Rhizobium

2. Azospirillum

3. Oscillatoria

4. Frankia

Which one of the following is not used in organic farming?

1. Glomus

2. Earthworm

3. Oscillatoria

4. Snail

An example of endomycorrhiza is:

1. Glomus

2. Agaricus

3. Rhizobium

4. Nostoc