Question

the first and most important signal of a serious head injury is—
a severe headache.
an altered level of consciousness.
the inability to breathe.
epileptic seizures.

Explanation:

A serious head injury often affects brain function, and an altered level of consciousness (e.g., confusion, loss of consciousness) directly indicates potential brain damage, making it the primary signal. Other options like severe headache or seizures may occur but are not as definitive or immediate a sign of severity as changes in consciousness. Inability to breathe is more linked to respiratory issues than head injury itself.

Answer:

B. An altered level of consciousness.