Two horizontal parallel plates each of area 500 cm2 are mounted 2mm apart in vacuum. The lower plate is earthed and the upper one
is given a positive charge of 0.05 uС. Find the electric field intensity
and the potential difference between the plates.

The answer is d) by requesting advice on science internet sites

Sublimation- which change of state is shown in model

Ohm's law tells you that i = v/r where v is equivalent voltage and r is equivalent resistance of the circuit
since all circuits have the same voltage, your question is really asking which circuit has the lowest total resistance, since the lower the resistance, the higher the current
circuit a has a resistance of 5 ohms; circuit c is in series so has a resistance of 10 ohms; circuit b is in parallel and therefore has a resistance of 2.5 ohms (review your notes on adding resistances in parallel and series); therefore b has the highest current