Concept:The leaf of an electroscope must be very light so it can be easily deflected by a small electric charge.
Explanation:In an electroscope, the metal leaf moves when it receives a charge.
For the leaf to show a clear deflection, it needs to respond to a weak electrostatic force.
A light material moves easily, so aluminium is chosen because it is light.
Being a good conductor is also necessary, but it is not the special reason for using aluminium as the leaf.
Aluminium can be rolled into thin sheets, but this property alone does not explain why it is used as a leaf.
The main reason is that its light weight allows the leaf to diverge readily when charged.
Answer:A. is a light material