As shown in the diagram, an electric circuit consisting of an ammeter, a voltmeter, 4 cells of $1\cdot 5\ \mathrm{V}$ each, a plug key with a gap XY was set up. Voltmeter and ammeter readings were recorded in the observation table for four arrangements as given below :

Arrangement No. 1 - only resistor $R_1$ in gap XY

Arrangement No. 2 - only resistor $R_2$ in gap XY

Arrangement No. 3 - Resistors $R_1$ and $R_2$ in series in gap XY

Arrangement No. 4 - Resistors $R_1$ and $R_2$ in parallel in gap XY

Based on the observations, four V-I graphs A, B, C and D as shown in figure were drawn. Study these graphs.

(a) Which one of the graphs represents the series combination of $R_1$ and $R_2$ ? [1]

(b) Which one of these graphs represents the parallel combination of $R_1$ and $R_2$ ? [1]

(c) (i) Show an arrangement of three resistors, each of resistance $10\ \Omega$, so that the combination has a resistance of $15\ \Omega$. Give justification for your answer. [2]

OR

(c) (ii) A battery of $6\ \mathrm{V}$ is connected with a series combination of five resistors of $0\cdot 1\ \Omega$, $0\cdot 2\ \Omega$, $0\cdot 3\ \Omega$, $0\cdot 4\ \Omega$ and $0\cdot 5\ \Omega$. How much current would flow through the $0\cdot 3\ \Omega$ resistor? Justify your answer. [2]