We need to match plant nutrients with their mobility characteristics or primary function. Nutrient mobility often refers to mobility within the plant (affecting where deficiency symptoms first appear) or mobility in the soil.
(A) Mn (Manganese):
Mobility in soil: Variable, generally less mobile, especially in alkaline or well-aerated soils.
Mobility in plant: Relatively immobile. Deficiency symptoms typically appear on younger leaves.
Function: Activates enzymes, involved in photosynthesis.
Matches with (II) "Less mobile" (referring to soil or general availability context).
(B) Mg (Magnesium):
Mobility in soil: Moderately mobile.
Mobility in plant: Highly mobile. Deficiency symptoms appear on older leaves first as Mg is translocated to new growth.
Function: Central component of chlorophyll, enzyme activator.
Matches with (I) "Highly mobile" (referring to plant mobility).
(C) Zn (Zinc):
Mobility in soil: Generally considered less mobile, availability affected by pH.
Mobility in plant: Intermediate to low mobility. Deficiency often affects younger leaves or overall growth.
Function: Component of enzymes, involved in auxin synthesis.
Matches with (II) "Less mobile" (referring to soil or general availability context).
(D) C (Carbon):
Not absorbed from soil as an ionic nutrient; taken from atmospheric CO\(_2\).
Function: Forms the backbone of all organic compounds (carbohydrates, proteins, fats, nucleic acids).
Matches with (IV) "Basic structure".
Therefore, the correct matching sequence is (A)-(II), (B)-(I), (C)-(II), (D)-(IV).
This corresponds to option (3).
(A) - (II), (B) - (I), (C) - (II), (D) - (IV)