Trevor, an engineer, supervises the construction of a new mountainside roadway. When the road collapses in a landslide due to faulty grading, Trevor is sued by motorists and hikers injured in the collapse. As a professional engineer, Trevor is held to the same standard of care as

a$.$ those injured in the collapse of the bridge.

b$.$ other professionals, including doctors, dentists, and lawyers.

c$.$ other engineers.

d$.$ ordinary persons.