Open Question
The specific relationship between a legume and its mutualistic Rhizobium strain probably depends ona. each legume having a chemical dialogue with a fungus.b. each Rhizobium strain having a form of nitrogenase that works only in the appropriate legume host.c. each legume being found where the soil has only the Rhizobium specific to that legume.d. specific recognition between chemical signals and signal receptors of the Rhizobium strain and legume species.