Final answer:
A strand test is the correct method to check if hair color is absorbing and processing evenly across a person's hair, by applying dye to a small section of hair.
Step-by-step explanation:
The test done to see if hair color is absorbing and processing evenly is a strand test. This test involves applying color to a small section of hair - typically from underneath and in an inconspicuous area - to ensure that the dye reacts properly. It allows for observation of the color development process and helps to predict the final outcome before applying the product to the entire head of hair. A patch test, also known as a skin allergy test, may be done before the strand test to ensure that there are no allergic reactions to the chemicals in the hair dye. A skin sensitivity test is similar to a patch test as it also checks for allergic reactions. However, these tests are not directly related to how the hair absorbs and processes color.