Assertion: Of all the mineral nutrients, nitrogen contributes the most to plant growth and crop yields.
Reason: Nitrogen is an essential macronutrient required by all plants.

1. Both assertion and reason are true and the reason is the correct explanation of the assertion.
2. Both assertion and reason are true but the reason is not the correct explanation of the assertion.
3. Assertion is true but reason is false.
4. Both assertion and reason are false.

1. If both the assertion and the reason are true and the reason is a correct explanation of the assertion
2. If both the assertion and reason are true but the reason is not a correct explanation of the assertion
3. If the assertion is true but the reason is false
4. If both the assertion and reason are false

Assertion: All nitrogen fixing organisms are bacteria.
Reason: Only bacteria can have mutualistic relationship with roots of plants.

1. Both assertion and reason are true and the reason is the correct explanation of the assertion.
2. Both assertion and reason are true but the reason is not the correct explanation of the assertion.
3. Assertion is true but reason is false.
4. Both assertion and reason are false.

Assertion: Nitrogen fixing bacteria require a rich supply of carbohydrates.
Reason: The process of nitrogen fixation requires 16 ATP molecules for every 2 ammonia molecules synthesized.

1. Both assertion and reason are true and the reason is the correct explanation of the assertion.
2. Both assertion and reason are true but the reason is not the correct explanation of the assertion.
3. Assertion is true but reason is false.
4. Both assertion and reason are false.

Assertion: Legume roots not colonized by Rhizobium do not synthesise leghemoglobin.
Reason: Some leguminous plants do not need nitrogen as an essential macronutrient.

1. Both assertion and reason are true and the reason is the correct explanation of the assertion.
2. Both assertion and reason are true but the reason is not the correct explanation of the assertion.
3. Assertion is true but reason is false.
4. Both assertion and reason are false.

Assertion: Oxygenic photosynthetic bacteria (cyanobacteria) generate oxygen as a by-product of photosynthesis, yet some are able to fix nitrogen as well.
Reason: These are colonial bacteria that have specialized cells (heterocysts) that lack the oxygen generating steps of photosynthesis.

1. Both assertion and reason are true and the reason is the correct explanation of the assertion.
2. Both assertion and reason are true but the reason is not the correct explanation of the assertion.
3. Assertion is true but reason is false.
4. Both assertion and reason are false.

Assertion: The mutualistic association between the fern Azolla and the cyanobacterium Anabaena azollae is important agriculturally.
Reason: The water fern Azolla harbouring Anabaena is an important green manure for rice culture.

1. Both assertion and reason are true and the reason is the correct explanation of the assertion.
2. Both assertion and reason are true but the reason is not the correct explanation of the assertion.
3. Assertion is true but reason is false.
4. Both assertion and reason are false.

Assertion: Elevated nitrate in groundwater is a concern for drinking water use.
Reason: Due to their very high solubility and because soils are highly unable to retain anions, nitrates can enter groundwater.

1. Both assertion and reason are true and the reason is the correct explanation of the assertion.
2. Both assertion and reason are true but the reason is not the correct explanation of the assertion.
3. Assertion is true but reason is false.
4. Both assertion and reason are false.

Assertion: Denitrification is the oxidation of nitrates back into nitrogen gas (N₂).
Reason: This process is performed by bacterial species such as Pseudomonas and Clostridium in aerobic conditions.

1. Both assertion and reason are true and the reason is the correct explanation of the assertion.
2. Both assertion and reason are true but the reason is not the correct explanation of the assertion.
3. Assertion is true but reason is false.
4. Both assertion and reason are false.

Assertion: Plant symbiont in Ectomycorrhizal mutualistic relationship form extensive root hair.
Reason: Ectomycorrhizas form between fungi and the roots of around 80% of plant species.

1. Both assertion and reason are true and the reason is the correct explanation of the assertion.
2. Both assertion and reason are true but the reason is not the correct explanation of the assertion.
3. Assertion is true but reason is false.
4. Both assertion and reason are false.

Assertion: Arbuscular Mycorrhizal are facultative symbionts.
Reason: These fungi have extensive saprobic capabilities.

1. Both assertion and reason are true and the reason is the correct explanation of the assertion.
2. Both assertion and reason are true but the reason is not the correct explanation of the assertion.
3. Assertion is true but reason is false.
4. Both assertion and reason are false.