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
All of the following are paired venous sinuses except 
Select and explain. 
A. Cavernous sinus., B. Inferior sagittal sinus., C. Inferior petrosal sinus., D. Sphenoparietal sinus.
B: Inferior sagittal sinus.
Answer: B: Inferior sagittal sinus. 
Explanation: None