Right choice is (b) k=\(\frac{1}{2}T_i^2(\vec{v}.\vec{v})\)
To explain I would say: To find the turbulent kinetic energy k using the turbulence intensity value, the following formula is used.
k=\(\frac{1}{2}T_i^2(\vec{v}.\vec{v})\)
Where,
\(\vec{v}\) → Velocity vector.