The largest reservoir of nitrogen in the global nitrogen cycle is the atmosphere. Options A-D below represent important pathways in the removal of nitrogen from the atmosphere at different rates.

A. Biological fixation in oceans
B. Fixation by lightning
C. Biological fixation in natural terrestrial systems
D. Industrial nitrogen fixation

Arrange the above pathways from the lowest to the highest rate.

Correct option is C

Explanation-

A. Biological fixation in oceans — Highest
Reason: Marine cyanobacteria (like Trichodesmium) fix large amounts of nitrogen. Oceans cover ~70% of Earth, offering vast areas for nitrogen fixation. Although individual rates are low, the global total is very high due to scale.
Highest nitrogen fixation rate

B. Fixation by lightning — Lowest
Reason: Lightning breaks N₂ into reactive nitrogen compounds (like NOx), but It's a rare, weather-dependent process and contributes less than 10 Tg N/year globally.
 Lowest among the listed

C. Biological fixation in natural terrestrial systems
Reason: Includes nitrogen-fixing bacteria in root nodules of legumes (e.g., Rhizobium). More active than lightning but less than oceans and industrial processes.
Intermediate in the list

D. Industrial nitrogen fixation
Reason: Through the Haber-Bosch process, converting atmospheric N₂ to ammonia (NH₃) can be used in fertilizer production; has grown rapidly due to agriculture. It fixes over 120 Tg N/year.
Less than oceans globally, but more than natural terrestrial fixation.
Second-highest

So, the correct order should be B<C<D<A (Option c)