A 4 kg block is pushed along the ceiling with a constant applied force of 85 N that acts at an angle of 55 degrees with the horizontal. The block accelerates to the right at 6 m/s^2. determine the coefficient of kinetic friction between the block and the ceiling.

  concave means having an outline or surface that curves inward like the interior of a circle or sphere. so the mirror curves inward.

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