Anyone Who Has Gone to a Dentist Has Seen the Drills

Anyone who has gone to a dentist has seen the drills they use in the first step of filling cavities.One of the major manufacturers of drills for dentists is XGT.In manufacturing its standard drill,it uses three components from other suppliers: an anti- retraction valve,a coupler- based swivel,and a fusion optics system for light.The sale of the anti- retraction valve partly depends on the availability of the lighting system and the swivel because demand for these products is _.

A) reciprocal
B) joint
C) synergistic
D) inelastic
E) elastic