The suggested answer is A.
After blocking a malicious URL found in an email, the next critical step would be to inform the CISO (Chief Information Security Officer) about the incident. This ensures that the organization's leadership is aware of the potential threat and can take necessary actions such as further investigation, response coordination, and communication with other stakeholders. Disabling the user's email account, confirming with the user, or changing the password are actions that depend on further assessment and instructions from the security team. Immediate notification to the CISO keeps the incident response process aligned with the organization's security policies and procedures.