Which of the following organisms does not fix $N_2$?

Choose the incorrect sentence.

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

Match the physiological processes given in Column-$I$ with the mineral elements given in Column-$II$:

Column-$I$	Column-$II$
$1$. Muscle contraction	$a$. $Mg^{+2}$
$2$. Digestion of food	$b$. $Ca^{+2}$
$3$. Energy exchange	$c$. $Mo$
$4$. Carbohydrate synthesis	$d$. $(PO_4)^{-3}$
$5$. Nitrogen fixation	$e$. $Cl^-$

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?

Select the correct option for the following matches:

$(1)$ For healthy growth of plants	$(a)$ Nitrogen
$(2)$ As a part of vitamins	$(b)$ Manganese
$(3)$ In enzymes associated with fat metabolism	$(c)$ Cobalt
$(4)$ For the activity of phosphatase enzyme	$(d)$ Magnesium