The correct option is D both a and b
The roots of leguminous plants have symbiotic association with nitrogen fixing bacteria, Rhizobium. Rhizobium infects the leguminous plants and forms nodules in the roots of these plants and thereby helps in nitrogen fixation.
In leguminous plants it was noticed that, when there is deficiency of boron, the Rhizobium bacteria infecting the host cells was reduced. Hence, boron deficiency can lead to a reduction in the number of nodules.
Sulphur is an essential constituent in proteins and the amino acids. It is very important for nodule development and efficient nitrogen fixation. Its deficiency leads to reduced number of nodules and reduced nodule metabolism and lead to impairment in working of nitrogenase synthesis and activity.