8.腦室系統的那一構造具有開口(aperture)，腦脊髓液可經由這些開口流入蜘蛛膜下腔(subarachnoid space)？ (A)左側腦室(left lateral ventricle) (B)右側腦室(right lateral ventricle) (C)第三腦室(third ventricle) (D)第四腦室(fourth ventricle)