Option A is correct. Both A and R are true, and R is the correct explanation of A. Reflex actions do not involve thinking because they are processed in the spinal cord (reflex arc), bypassing the brain.
The textbook states that reflex arcs are formed in the spinal cord itself, allowing quick responses without involving the brain's thinking process. Since the spinal cord handles reflex actions, thinking (a brain function) is not required — making R the correct explanation of A.