$\mathbf{\text{Step}}\mathbf{\text{-}}\mathbf{\text{1:}}\mathbf{\text{Calculating}}\mathbf{\text{outcomes}}$

                  $\text{Favorable outcomes i.e., getting tail = 1}$

                  $\text{Total number of outcomes [H, T] = 2}$

$\mathbf{\text{Step}}\mathbf{\text{-}}\mathbf{\text{2:}}\mathbf{\text{Finding}}\mathbf{\text{Probability,}}$

                 $\mathbf{\text{The}}\mathbf{\text{formula}}\mathbf{\text{for}}\mathbf{\text{probability}}\mathbf{\text{=}}{\displaystyle \frac{\mathbf{\text{favorable}}\mathbf{\text{outcome}}}{\mathbf{\text{total}}\mathbf{\text{number}}\mathbf{\text{of}}\mathbf{\text{outcome}}}}$

                  $\text{Required probability = }{\displaystyle \frac{1}{2}}$

$\mathbf{\text{Hence}}\mathbf{\text{,}}\mathbf{\text{the}}\mathbf{\text{required}}\mathbf{\text{probability}}\mathbf{\text{is}}\mathbf{\text{(D)}}{\displaystyle \frac{\mathbf{1}}{\mathbf{2}}}$