What is nutrient immobilisation?

Which of the following options shows the correct correlation between column $I$,$II$,and $III$?

Column $I$	Column $II$	Column $III$
$A$. Calcium	$I$. Required for ionic balance	$(i)$. Grey blot on leaves
$B$. Boron	$II$. Essential for constitution of nucleic acid	$(ii)$. Fruit-yield decreases
$C$. Phosphorus	$III$. Required for absorption of calcium	$(iii)$. Red blot on leaves
$D$. Chlorine	$IV$. Required to activate respiratory enzyme	$(iv)$. Fruit-size diminishes
$E$. Manganese	$V$. Required for synthesis of mitotic spindle	$(v)$. Young root tip begin to die

Which of the following is a free-living nitrogen-fixing bacterium?

Consider the following statements regarding mineral nutrition:
$(a)$ Moderate decrease or increase of micronutrients causes deficiency and toxicity symptoms respectively.
$(b)$ Excess of manganese causes toxicity of iron, calcium and molybdenum.
$(c)$ $A$ macronutrient is said to be toxic when present below a critical concentration.
Which of the above statements are correct?

The soil organisms are

Which one of the following is a wrong statement?