(a)[3]
Explain what the term nitrogen fixation means.
(b(i))[1]
State the name given to this process in the nitrogen cycle.
(b(ii))[2]
Explain why this process is important for making nitrogen from animals available for plant uptake.
(c(i))[1]
State how Tube C serves as a control in this investigation.
(c(ii))[4]
Explain the difference in the results for Tube A and Tube B.