Which graph in Fig. $\mathbf{P} 29.74$ best represents the time $t$ dependence of the current $i$ induced in the brain tissue, assuming that this tissue can be modeled as a resistive circuit? (The units of $i$ are arbitrary.) (a) $\mathrm{A} ;$ (b) $\mathrm{B} ;$ (c) $\mathrm{C} ;$ (d) $\mathrm{D}$.