(a(i))[2]
State the names of any two stages in sewage treatment.
(a(ii))[1]
State the name of one additional source of water pollution.
(b(i))[1]
State the name of the biological molecules that are broken down to make urea.
(b(ii))[1]
State the name of the organ that produces urea.
(c)[2]
State two further negative effects of intensive livestock farming.