myelography is diagnostic examination used to demonstrate.. extrinsic spinal cord compression resulting from disk herniation

myelography is diagnostic examination used to demonstrate
1- extrinsic spinal cord compression resulting from disk herniation
2- post-traumatic swelling of the spinal cord
3- internal disk lesions
a. one only
a. 1 and 2 only
b. 1 and 3 only
c. 1,2 and 3