Which of the following is considered to be the best chemical method of fixing atmospheric nitrogen?

Analogy type questions:
$(1)$ Nitrogenase : Oxygen sensitive :: Leghaemoglobin : ........
$(2)$ Microbe on roots of Alnus : Frankia :: Roots of leguminous plants : Rhizobium :: Denitrification : Pseudomonas :: Biological nitrogen fixation : ........

In which of the following conditions,plants cannot be grown?

Which of the following plants is used as green manure in crop fields and in sandy soils?

Match the columns:
$I$ $II$
$(A)$ Magnesium $(i)$ Found in middle lamella
$(B)$ Sulphur $(ii)$ $A$ structural component of chlorophyll
$(C)$ Calcium $(iii)$ Required for enzyme activity
$(D)$ Iodine $(iv)$ Found in some amino acids
$(E)$ Manganese $(v)$ $A$ component of sugars
$(vi)$ Not important for plants

Select the correct option:
$(1)$ During $transamination$ / $reductive$ $amination$,an amino group is transferred from one amino acid to the keto group of a keto acid.
$(2)$ $Azotobacter$ / $Clostridium$ are free-living bacteria.