A capacitor is charged and then made to discharge through a resistance. The time constant is $\tau$. In what time will the potential difference across the capacitor decrease by 10%

Question

$\begin {array} {1 1} (A)\;\tau \: ln (0.1) & \quad (B)\;\tau \: ln (0.9) \\ (C)\;\tau \: ln \bigg(\large\frac{10}{9}\bigg) & \quad (D)\;\tau \: ln \bigg(\large\frac{11}{10}\bigg) \end {array}$