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1. |
When items of jewellery made of metals such as copper or nickel are placed in a solution having a salt of gold, a thin film of gold is deposited by..... |
A. | passing an electric current |
B. | cooling to below 0 degree C |
C. | heating above 100 degree C |
D. | just keeping it for 10 minutes |
Answer» B. cooling to below 0 degree C | |