Answer:
Choice A. 
electrons would be required for displacing 
of aluminum from a solution of 
ions.
Assumption: by "
ions" the question meant 
with a charge of 
on each ion.
Explanation:
The question states that the relative atomic mass of is 
. In other words, each mole of
Therefore, that 
of silver that were formed would contain 
of silver atoms.
Metallic silver would precipitate out of this solution only after these ions are turned into atoms.
One ion carries one unit of positive electrical charge. On the other hand, each 
carries one unit of negative electrical charge.
Therefore, each 
ion will need to gain one electron to form a neutral atom.
.
At least of electrons would be required to turn 
of ions into that 
of silver atoms (which have a mass of .)
Hence, 
.
Unlike ions, each aluminum ion carries three units of positive electrical charge. That is three times the amount of charge on one ion. Therefore, three electrons will be required to turn one 
ion to an 
atom.
The question states that the relative atomic mass of is 
. Therefore, each mole of 
atoms would have a mass 
. There would be 
of atoms in that of 
.
It takes 
of electrons to turn one mole of ions to one mole of atoms. Hence, 
of electrons would be required to produce that 
of atoms (which has a mass of ) from ions.
That corresponds to the first choice, electrons.
