Read this and answer the question. If the question is unanswerable, say "unanswerable".

Following Garreth Mallory's promotion to M, on a mission in Mexico City unofficially ordered by a posthumous message from the previous M, 007 James Bond kills three men plotting a terrorist bombing during the Day of the Dead and gives chase to Marco Sciarra, an assassin who survived the attack. In the ensuing struggle, Bond steals his ring, which is emblazoned with a stylised octopus, and then kills Sciarra by kicking him out of a helicopter. Upon returning to London, Bond is indefinitely suspended from field duty by M, who is in the midst of a power struggle with C, the head of the privately-backed Joint Intelligence Service, consisting of the recently merged MI5 and MI6. C campaigns for Britain to form alongside 8 other countries "Nine Eyes ", a global surveillance and intelligence co-operation initiative between nine member states, and uses his influence to close down the '00' section, believing it to be outdated.

Who is M's rival?
C