Final answer:
The capacitance of a parallel-plate capacitor is influenced by the area of the plates and the distance between them. In this case, the capacitor with the smallest plate separation will store the most charge on the top plate. Option 1.
Step-by-step explanation:
The capacitance of a parallel-plate capacitor depends on the area of the plates (A) and the distance between them (d).
According to the Coulomb force, larger plates can store more charge, so the capacitance (C) should be greater for a larger plate area.
Additionally, the closer the plates are together, the greater the attraction of the opposite charges, resulting in a greater capacitance for a smaller plate separation.
In this case, all capacitors have the same plate area (a=a) but different plate separations (d, 2d, 3d, 4d).
Therefore, the capacitor with the smallest plate separation (d) will store the most charge on the top plate for a given potential difference (v).
Hence, the right answer is option 1.