Choose the correct answer from options given
below.
(a) (b) (c) (d)
(1) (ii) (iv) (i) (iii)
(2) (i) (ii) (iii) (iv)
(3) (iii) (i) (iv) (ii)
(4) (iv) (iii) (ii) (i)

Correct option:(1)
Solution:

• Nitrogen fixation is conversion of atmospheric N2 to NH3 (ammonia).
• It is carried out by N2 fixers such as Rhizobium.
• NH3 is converted to – NO (nitrite) 2 by nitrifying bacteria such as Nitrococcus.
• NO2 is converted to NO3 (nitrate)  by nitrfying bacteria called Nitrobacter.
• Thiobacillus carries out denitrification, a process where NO / NO2 is converted to N2.