The differential equation $$\frac{{{\text{dx}}}}{{{\text{dt}}}} = \frac{{4 - {\text{x}}}}{\tau },$$   with x(0) = 0 and the constant $$\tau $$ > 0, is to be numerically integrated using the forward Euler method with a constant integration time step T. The maximum value of T such that the numerical solution of x converges is

A. $$\frac{\tau }{4}$$

B. $$\frac{\tau }{2}$$

C. $$\tau $$

D. $$2\tau $$

Answer: Option D