Which of the following are unpaired vessel in CNS--: (A) Anterior cerebral artery, (B) Basilar artery, (C) Posterior cerebellar artery, (D) Posterior communicating artery
Answer is B. Basilar artery  is single unpaired vessel, it is formed by right and left vertebral arteries, at lower border of pons and ends at upper border of pons by dividing into right and left posterior cerebral arteries.