Upregulation of Leghemoglobin Biosynthesis in a Leguminous Species Would Most

Upregulation of leghemoglobin biosynthesis in a leguminous species would most likely indicate

A) the plant is suffering from a mineral deficiency.
B) the successful inoculation of nitrogen-fixing bacteria.
C) the plant is suffering from water stress.
D) the plant has been infected with mycorrhizae.
E) an increase in the biosynthesis of amino acids.