Question

1. the value for i_n equals the current through

a terminals a and b
b terminals a and b with a short - circuit across them
c r1 to terminal a
d r1 to terminal a with r1 short - circuited

Explanation:

The Norton current ($I_N$) is defined as the current that flows through the short - circuit placed across the terminals of interest. In this case, the terminals of interest are A and B. So, $I_N$ is the current through terminals A and B when they are short - circuited.

Answer:

B. terminals A and B with a short - circuit across them