Final answer:
The correct answer is Kernig's sign, which is a clinical sign indicating potential meningitis by the inability to fully extend the leg and/or presence of neck pain.
Step-by-step explanation:
The symptom described as the inability to fully extend the leg and/or pain usually in the neck region indicating meningeal irritation or meningitis is known as Kernig's sign. This neurological sign is used by physicians to diagnose conditions like meningitis. Brudzinski's sign is another closely related sign where neck flexion in a supine patient leads to reflex flexion of the hips. On the other side we have the Babinski sign, which is the dorsiflexion of the foot with extension and splaying of the toes in response to the plantar reflex, commonly associated with upper motor neuron damage. The Lasegue's sign is associated with sciatic nerve irritation and reproduced by straight leg raising. None of these other signs specifically indicate meningeal irritation or meningitis.