Nitrate present in the soil is reduced to nitrogen by the process of denitrification. Which bacteria are responsible for denitrification?

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?

Identify the mismatched pair.

Match the following and choose the correct combination from the options given.

Column $I$	Column $II$
$a.$ Potassium	$(i)$ Germination of pollen grains
$b.$ Molybdenum	$(ii)$ Involved in synthesis of auxin
$c.$ Boron	$(iii)$ Involved in stomatal movement
$d.$ Zinc	$(iv)$ Constituent of ferredoxin
$e.$ Sulphur	$(v)$ Component of nitrate reductase

Ammonium sulphate is:

The agent/s which make/s free atmospheric nitrogen available to plants is/are: