a b c d

b

$ I = I_0 (1 - e^\frac{-t}{\tau}) \tau = \frac{L}{R} = 0.5 $ $\text{ as } t \to \infty I_1 = I_0$ $\text{ as } t = 1,  I_2 = I_0(1- e^2)$ $ \frac{I_1}{I_2} = \frac{e^2}{e^2-1}$