(i) V=IR, where V is potential difference, I is current and R is constant for a given resistor as its resistance. Hence, current I is directly proportional to V.(ii) An ammeter have low resistance, so that it does not hinder and alter the flow of electric current and easily allow all the current to flow through the circuit without energy wastage due to heat losses.
(iii) We know that V=IR or ‌

1

R

=‌

I

V

= slope of graph given. Lower the slope, higher is the resistance. Clearly, graph B has higher slope than A. Therefore resistance of B is lower than that of A. We know that combined series resistance is always higher than the combined parallel resistance. Hence, A is series combination and B is parallel combination.