The best answer is B. An attacker viewed password hashes on the device . The decisive event is sudo cat /etc/shadow SUCCESS . On Linux systems, /etc/shadow stores password hashes and related account password data. The log therefore indicates successful privileged access to that file and successful viewing of its contents. CompTIA’s SecurityX Security Operations domain includes analysis of indicators of malicious activity and investigation of suspicious system behavior; this command sequence is consistent with credential-access activity.

Why the other options are not best:

A is incorrect because there is no evidence of file injection. C is not supported because the logs show file access, not confirmed data transfer or exfiltration. D is tempting because of cd ../../ , but that is only navigation. The key security-relevant action is the successful reading of /etc/shadow , which means password hashes were viewed.