The correct option is D aqueduct of Sylvius
The brain is divided into three parts, namely, the forebrain, midbrain and the hindbrain. The cerebrum of the forebrain is divided into two halves, namely, the left and the right cerebral hemispheres. The brain consists of four ventricles in total. Each cerebral hemisphere contains one ventricle. These ventricles are called the lateral ventricles. The diencephalon part of the forebrain contains the third ventricle. The hindbrain contains the fourth ventricle. The third and fourth ventricles of the brain are connected by cerebral aqueduct, which is a canal that passes through the midbrain. It is also known as the aqueduct of Sylvius.