Sympathetic fibers leave the spinal cord in the ________.

A) cranial and sacral regions
B) lumbar and sacral regions
C) cranial and thoracic regions
D) thoracic and lumbar regions
E) cervical and sacral regions

Sympathetic fibers, part of the sympathetic nervous system, exit the spinal cord in the thoracic and lumbar regions, specifically from the first thoracic (T1) to the second or third lumbar (L2 or L3) vertebrae. This part of the autonomic nervous system is responsible for the body's "fight or flight" response.