Final answer:
The principle of continuity explains how Sinead knows that the snake is not broken into individual segments.
Step-by-step explanation:
The correct answer is a) principle of continuity. According to Gestalt psychology, Sinead knows that the snake is not broken into individual segments because of the principle of continuity. This principle suggests that we are more likely to perceive continuous, smooth flowing lines rather than jagged, broken lines. In this case, Sinead perceives the snake as a whole because it appears as a continuous line.