A resistance $R$ and a capacitance $C$ are connected in series to a battery of negligible internal resistance through a key. The key is closed at $t=$ 0 . If after $t$ sec the voltage across the capacitance was seven times the voltage across $\mathrm{R}$, the value of $\mathrm{t}$ is

• Correct answer
  A

  $3 R C \ell n 2$
• B

  $2 R C \ell n 2$
• C

  $2 R C \ln 7$
• D

  $3 R C \ell n 7$

Hence, the correct answer is option: 'A'.