Lactose is a disaccharide composed of one molecule of \( \beta \)-D-galactose and one molecule of \( \alpha \)-D-glucose. These two sugars are linked by a β-1,4-glycosidic bond, which is hydrolyzed by lactase in the human body.
Samples of four metals A, B, C, and D were added one by one to the following solutions. The results obtained were tabulated as follows:
Use the table above to answer the following questions about metals A, B, C, and D:
(i) Which is the least reactive metal?
(ii) What would be observed if C is added to a solution of copper sulphate?
(iii) Arrange the metals A, B, C, and D in the order of their decreasing reactivity.