Test tube A:
Iron sulphate is a green coloured solution. However, the resultant aluminium sulphate is colourless.
Test tube B:
Copper sulphate is a blue coloured solution. However, the resultant aluminium sulphate is colourless.
Test tube C:
No reaction takes place here because aluminium is more reactive than iron.
Test tube D:
Here, iron replaces copper and form ferrous sulphate which is a pale green coloured solution because iron is more reactive than copper.
Colour changes were observed in test tubes A, B and D.
Therefore, reactivity in decreasing order is: Al > Fe > Cu
Aluminium is the most reactive metal because it displaced both iron and copper from their compounds.
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