I believe it is A because the plant is offering protection while the bacteria is converting it in to nitrogen that the plant can use!
No it does not effect the temperature of boiling point
The atomic number, the number of protons and the number of electrons.
a) The change here is that metallic iron is converted into ions and copper is deposited. This is called a displacement reaction.
b) is oxidised in this reaction.
c)$ \mathrm{Fe_{(s)}+ CuSO_{4(aq)} \rightarrow FeSO_{4(aq)} + Cu_{(s)}}$