Root nodules are associations between bacteria and plant roots responsible for

Root nodules are associations between bacteria and plant roots responsible for nitrogen fixation.

Explanation:

the number of protons in the nucleus of a given element. has slight luster and conducts electricity at high temperatures like metal.but like a nonmetal,boron is brittle and does not conduct electricity well at low temperatures. in graphite, carbon is a soft,brittle solid.it is reflective,ductile,or malleable.