North Dakota Barber Practice Exam

The other options, including density test, finger test, and pull test, are not necessary for determining the expected results from a straightening treatment. The density test is used to determine the density or thickness of the hair, which is not necessarily related to the expected results of a straightening treatment. The finger test involves running your fingers through the hair to check for tangles or damage, but it is not specifically relevant to the expected results of a straightening treatment. The pull test is used to check the strength and elasticity of the hair, which is also not directly related to determining the expected results of a straightening treatment. The correct option, C, suggests that a relaxer test is necessary, as it is used to test the hair's reaction to the straightening chemicals and assess the expected outcome of the treatment.