in rutherinto the forest Alpha particle scattering experiment with their code for 8100 scintillations per minute are observed at an angle of 60 degree then number of scintillations per minute at 120 degree will be

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

Since the pully is a simple machine so the mechanical advantage is a 1

Work is reduced while time is decreased