Leghaemoglobin is useful for legumes because it
A. irreversible absorbs `O_(2)` which inhibit `N_(2)`-fixation
B. reversible absorbs `O_(2)` which inhibit `N_(2)`-fixation
C. protects plant tissues from damage by symbiotic bacteria
D. absorbs `O_(2)` at low oxygen tension and provides it to the tissue surrounding `N_(2)`-fixing bacteria
