If XXX and YYY are independent and Z=X+YZ = X + YZ=X+Y, then the characteristic function ϕZ(t)\phi_Z(t)ϕZ(t) is:
ϕX(t)/ϕY(t)\phi_X(t) / \phi_Y(t)ϕX(t)/ϕY(t)
ϕX(t)⋅ϕY(t)\phi_X(t) \cdot \phi_Y(t)ϕX(t)⋅ϕY(t)
ϕX(t)+ϕY(t)\phi_X(t) + \phi_Y(t)ϕX(t)+ϕY(t)
None of the above