Hinsberg's reagent is :

In an acid-base titration, 0.1 M HCl solution was added to the NaOH solution of unknown strength. Which of the following correctly shows the change of pH of the titraction mixture in this experiment?

The correct statements among I to III are :
(I) Valence bond theory cannot explain the color exhibited by transition metal complexes.
(II) Valence bond theory can predict quantitatively the magnetic properties of transtition metal complexes.
(III) Valence bond theory cannot distinguish ligands as weak and strong field ones.

Which of the following compounds is a constituent of the polymer