The correct option is
B Choroid
A. Sclera is the external layer of eye which maintains the shape of eye and also protects it.
B. Choroid is the middle layer of eye which contains many blood vessels and appears bluish in colour. It forms the vascular coat or layer of eye.
C. Retina is present in the inner layer of eye which contains ganglion cells, bipolar cells and photoreceptor cells.
So, the correct answer is 'Choroid'.