Final answer:
The NIST CyberSecurity framework defines five core security functions: Identify, Protect, Detect, Respond, and Recover. 'Contain' is not one of these core functions, making it the correct answer to the question.
Step-by-step explanation:
The question asks which of the following is not one of the five core security functions defined by the NIST CyberSecurity framework. The correct answer is B. Contain. The NIST CyberSecurity framework outlines five core functions which are: Identify, Protect, Respond, Recover, and Detect. 'Contain' is not listed as one of these core functions. Instead, 'Contain' is more commonly associated with incident response procedures following a cybersecurity incident to limit the extent of the damage.