The principle encourages us to resolve a set of stimuli, such as trees across a ridgeline, into smoothly flowing patterns

If this question has the same set of options as to the following, the answer would be letter d. Continuity.
Continuity in Psychology accounts for visual perception of immediate environments that piece together a background's individual elements to form a panoramic image. 

The choices are:
A.) depth perception. 
B.) perception. 
C.) similarity. 
D.) continuity.

Why the rest of the question?

1) when you rub your hands together quickly, the kinetic energy is converted to mechanical energy.2) thermal energy from the sun travels to earth as infrared waves.3) energy is transferred through the matter of space by electromagnetic waves. 4) when a match is burned, chemical potential energy is converted to thermal and radiant energy. 5) seismicwaves are caused by back and forth movement , or vibration, of an object. 6) mechanicalenergy in an engine changes thermal energy into kinetic energy to make a car move.