(a) 2HNO3 + Ca(OH)2 \(→\) Ca(NO3)2 + 2H2O
(b) 2NaOH + H2SO4 \(→\) Na2SO4 + 2H2O
(c) NaCl + AgNO3 \(→\) AgCl + NaNO3
(d) BaCl2 + H2SO4 \(→\) BaSO4 + 2HCl
(i) Study the diagram and name the parts marked as A, B, C, and D.
(ii) Write the function of A and C.