Final answer:
Failing to safeguard Delta SSI materials includes sharing sensitive information with unauthorized individuals. Other listed options such as securing documents, encrypting digital files, and conducting security training are proper safeguarding measures.
Step-by-step explanation:
Examples of failing to safeguard Delta Sensitive Security Information (SSI) materials include behaviors that allow these materials to be accessed by unauthorized individuals or entities, or otherwise compromise the security of the information. One such example is B) Sharing sensitive information with unauthorized individuals. This action directly contradicts the necessary precautions required to maintain the confidentiality and integrity of Delta SSI materials. The other options: A) Properly securing documents in a locked cabinet, C) Encrypting sensitive digital files, and D) Conducting regular security training, all represent appropriate and responsible measures taken to protect sensitive information.