Match the following:

A. Leaching is used to extract \( \text{Al}_2 \text{O}_3 \) from bauxite.
B. Mond process is used for extracting Nickel (Ni).
C. Van Arkel method is used to obtain pure Zirconium (Zr).
D. Zone refining is used for the purification of Indium (In).
Thus, the correct matching is:
The electrolyte which is highly effective for the coagulation of antimony sulphide sol is:
The Tyndall effect is observed only when the following conditions are satisfied: