Etruscan Railing Company Makes Railing That Is Used in Sports

Etruscan Railing Company makes railing that is used in sports arenas,nursing home corridors,queue houses at amusement parks,and many other places that are not as obvious.Its railing is moulded into bicycle racks.You may also see city governments using the railing to make walkways over ravines and creek banks safer for pedestrian traffic.Hospitals also use the railing in their physical therapy departments,to keep the lines straight in the hospital cafeteria,and to prevent patients from falling out of hospital beds.
-Refer to Etruscan Railing Company.Etruscan has experienced a strong increase in railing sales as a result of the growth of school football.Which type of demand is this increase for railings as a result of the need for new football stadiums?

A) joint
B) derived
C) inelastic
D) fluctuating