Question

the butterfly-shaped cranial bone that spans the width of the cranium is the:
ethmoid
sphenoid
parietal
frontal

Explanation:

The ethmoid is a small, delicate bone in the nasal cavity area, not butterfly-shaped or spanning the cranium width. The parietal bones are paired, flat bones forming the top and sides of the cranium, not butterfly-shaped. The frontal bone forms the forehead, a single flat bone at the front of the skull. The sphenoid bone is a single, butterfly-shaped cranial bone that sits at the base of the skull and spans its width.

Answer:

sphenoid