Study the cycle shown below and select the option which gives correct words for all the four blanks A, B, C and D:
            

	(A)	(B)	(C)	(D)
1.	Denitrification	Ammonification	Plant  biomass	Animal biomass
2.	Nitrification	Denitrification	Animal biomass	Plant  biomass
3.	Denitrification	Nitrification	Plant biomass	Animal biomass
4.	Nitrification	Ammonification	Animal biomass	Plant biomass

Leguminuous plants are able to fix atmoshpheric nitrogen through the process of symbiotic nitrogen fixation. Which one of the following statement is not correct during this process of nitrogen fixation ?
1. Nodules act as sites for nitrogen fixation
2. The enzyme nitrogenase catalyses the conversion of atmospheric N₂ to NH₃
3. Nitrogenase is insensitive to oxygen
4. Leghamoglobin scavenges oxygen and pinkish in color.

The most abundant intracellular cation is:
1. ${\mathrm{Na}}^{+}$
2. ${\mathrm{Ca}}^{++}$
3. ${\mathrm{H}}^{+}$
4. ${\mathrm{K}}^{+}$

Assertion: Negatively charged ions in soils are more easily lost by leaching than positively charged ions.
Reason: Soil particles in most productive soils are positively charged.

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: High acidic soils can present problems for plant growth.
Reason: At low pH, aluminum ions toxicity becomes important.

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: In some cases, sodium may be a ninth essential micronutrient.
Reason: Essential micronutrients are needed by the plants only in tiny quantities.

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: Micronutrients function in plants mainly as cofactors.
Reason: Iron is a metallic component of cytochromes.

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: Iron deficiency in plants can cause chlorosis.
Reason: Iron is a component of chlorophyll.

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: A plant deficient in magnesium first shows signs of chlorosis in older leaves.
Reason: If a nutrient moves about freely, symptoms appear first in older organs.

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: Young seedlings frequently show mineral deficiency symptoms.
Reason: Their requirement is much lower than the requirements of older plant parts.

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.