Final answer:
Cross-checking is the technique used to ensure haircut precision, good continuation refers to the perceptual law that helps the eye follow smooth lines, and hatching is a technique for showing shading and three-dimensionality.
Step-by-step explanation:
The technique used to check a haircut for precision of line and shape is called C) Cross-checking. Cross-checking is the process of checking the haircut from different angles to ensure that the hair is evenly cut and that the lines and layers are precise. When cross-checking, the stylist may use a mirror or look at the profile to see the balance of the haircut and make any necessary corrections. This process helps to achieve a balanced and symmetrical haircut, contributing to a polished and professional finished look.
As for the question related to the law of perception in regard to lines, the law often associated with creating a sense of continuity and smoothness in visual elements is B) good continuation. This law suggests that elements arranged in a straight line or a smooth curve are perceived as belonging together, and the eye will follow these elements in a path even when other visual interruptions may appear.
In regards to showing shading and shadows, techniques such as hatching can be used to depict light and shadow. This use of lines is an essential tool for artists to create the illusion of three-dimensionality, giving objects a sense of form and depth as mentioned with the hat illustration.