Which among the following is the best example of the hacking concept called "clearing tracks"?

A. An attacker gains access to a server through an exploitable vulnerability.
B. During a cyberattack, a hacker injects a rootkit into a server.
C. After a system is breached, a hacker creates a backdoor to allow re-entry into a system.
D. During a cyberattack, a hacker corrupts the event logs on all machines.