Correct Answer. B. Change their password immediately Changing the password immediately after noticing an unauthorized access attempt is a crucial first step in safeguarding the account from potential compromise.
Option A is incorrect because ignoring the attempt may lead to future successful breaches.
Option C is incorrect as shutting down the computer does not address the security of the online account.
Option D is incorrect because while deleting suspicious emails might be helpful, it does not secure an account that has already been targeted.