What can the System Administrator do to trouble shoot this issue?

When a Sales Representative creates a lead, a workflow rule should be triggered to immediately send a welcome email to the lead. Some representative report that their leads never received this email, even when the email address is correct.

What can the System Administrator do to trouble shoot this issue?
A . Monitor the time-based workflow queue to make sure the emails are being sent
B . Monitor Setup Audit Trail while Sales Representative creates lead to make sure emails are being sent
C . Monitor the Debug Log and verify that the workflow rule is being triggered.
D . Ensure that Sales Representative have correct permissions to trigger workflow rules

Answer: C