Richard, an engineer, supervises the construction of a new mountainside roadway. When the road collapses in a landslide due to faulty grading, Richard is sued by motorists and hikers injured in the collapse. As a professional, Richard is held to the same standard of care as:_______.a. ​ordinary persons.
b. ​other engineers.
c. ​other professionals, including doctors, dentists, and lawyers.
d. ​those injured in the collapse of the bridge.