This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Anatomy
Greater vein of Galen is formed by : 
Select and explain. 
A. Superior saggital sinus with straight sinus, B. Inf. saggital sinus with straight sinus, C. Internal cerebral veins, D. Basilar vein
C: Internal cerebral veins
Answer: C: Internal cerebral veins 
Explanation: C. i.e. Internal cerebral veins