Answer: C) Man-in-the-middle
Step-by-step explanation: Man-in-the-middle attack is the attack where the hacker or attacker receives and passes on communication by manipulating it between victim and entity. These two parties have the middle-man who can alter the communication secretly , without the knowledge of other parties.
The situation mentioned in the question is also similar where the every certificate on network seems to be signed ,which was not communicated or done by the proxy server or network administrator actually.
Other options are incorrect because transitive access is misusing the access and control leading to information risk. Spoofing is disguising of hacker into reliable device for hacking information. Replay is the playing the content again in repetition.Thus , the correct option is option(C).