Answer:
C. Man-in-the-middle; well-controlled storage of private keys.
Step-by-step explanation:
During the forensic phase of a security investigation, it was discovered that an attacker was able to find private keys on a poorly secured team shared drive, thus describing a well-controlled storage of private keys.
The attacker using those keys to intercept and decrypt sensitive traffic on a web server is a Man-in-the-middle attack.