Which of the following bacteria are free-living nitrogen fixers?

Which of the following is a free-living nitrogen-fixing bacterium present in the soil?

Which mineral element plays an important role in biological nitrogen fixation?

Which of the following is a free-living,aerobic,and non-photosynthetic nitrogen-fixing bacterium?

Which of the following is/are diazotrophs?

Categorize the following nitrogen-fixing microorganisms into symbiotic and free-living types:
$I-$ Rhizobium
$II-$ Azotobacter
$III-$ Beijerinckia
$IV-$ Rhodospirillum
$V-$ Frankia
$VI-$ Bacillus
$VII-$ Anabaena (free-living)
$VIII-$ Nostoc (symbiotic)
Select the correct grouping for (Symbiotic) and (Free-living) respectively.