The correct answer is A) 'R1', 'R2', and 'R3' are connected in series. In a series circuit, the components are connected end-to-end, forming a single path for the current to flow. The total resistance in a series circuit is the sum of the individual resistor values, which is consistent with the illustration. The other options are incorrect because: B) The total resistance in a series circuit is not the reciprocal of the sum of the reciprocals of the individual resistors. C) The resistors are not connected in parallel, as they do not have the same voltage across them. D) The voltages measured across series-connected resistors are not necessarily equal, as the current is the same through each resistor but the resistor values may differ.