Answer : Option B

Explanation :

Let principal be P
$MF#%\begin{align}&\text{P}\left(1 + \dfrac{\text{R}}{100}\right)^\text{T} > 2P\\\\ &\text{P}\left(1 + \dfrac{20}{100}\right)^\text{T} > 2P\\\\ &\left(1 + \dfrac{20}{100}\right)^\text{T} > 2\\\\ &\left(\dfrac{120}{100}\right)^\text{T} > 2\\\\ &1.2^\text{T} > 2\end{align}$MF#%
Now let's find out the minimum value of T for which the above equation becomes true
If T = 1, 1.2^T = 1.2¹ = 1.2
If T = 2, 1.2^T = 1.2² ≈ 1.4
If T = 3, 1.2^T = 1.2³ ≈ 1.7
If T = 4, 1.2^T = 1.2⁴ ≈ 2.07 which is greater than 2
Hence T = 4
i.e., required number of years = 4