Final answer:
The best first step to take when a supervisor expresses interest in terminating an employee due to ongoing performance issues is to check the personnel record for documentation of previous and current performance issues.
Step-by-step explanation:
The best first step to take when a supervisor expresses interest in terminating an employee due to ongoing performance issues is to check the personnel record for documentation of previous and current performance issues (option C).
By reviewing the personnel record, the HR leader can gather objective evidence of performance issues and assess the severity and consistency of the problems. This step is crucial in making informed decisions about termination and ensuring fairness in the process.
Options A and B are not appropriate in this situation as they involve actions unrelated to the employee's performance issues, and option D is incorrect because performance issues typically require action and intervention to be resolved.