(d) $A$ is involuntary. Hence, $A^{2} = I \Rightarrow A = A^{- 1}$ Also, $(kA)^{- 1} = \frac{1}{k}(A)^{- 1}$ $\Rightarrow \left( \frac{1}{2}A \right)^{- 1} = 2(A)^{- 1} \Rightarrow 2A$
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.