The correct option is
B Floor of lateral ventricle
The lateral ventricles lie within the cerebral hemisphere. The cross-section of the lateral ventricle reveals the roof, floor and median wall. The roof is made up of the corpus callosum. The wall is made up of the septum pellucidum. The floor is made up of the corpora striata which contain the caudate nucleus and the lentiform nucleus.
Hence, the correct answer is 'Floor of the lateral ventricle'