For detecting the nitrites in the sewage, the matching colour may be developed by adding_________________?

A. supersonics, as with projectile and jet propulsion
B. full immersion or completely enclosed flow, as with pipes, aircraft wings, nozzles etc.
C. simultaneous motion through two fluids where there is a surface of dis-continuity, gravity forces, and wave making effect, as with ship’s hulls
D. all of the above
E. none of the above