Under Semi-Infinite Boundary Conditions, for a Simple Electron Transfer Reaction $$\pm \pi$$

Under semi-infinite boundary conditions, for a simple electron transfer reaction, the concentration oscillations and current oscillations have a phase offset (in radians) of

A) $$\pm \pi$$
B) 0
C) $$\frac { \pm \pi } { 2 }$$
D) $$\frac { \pm \pi } { 4 }$$