During preflight you notice the airworthiness certificate is faded, torn, and unreadable. What actions must you take? Can you legally operate the aircraft?
a) Replace the certificate; Yes, if other documentation is in order
b) Contact the FAA; No, obtain a new certificate before flying
c) Ignore it; Yes, as long as the aircraft appears airworthy
d) Continue with the flight; No, suspend the flight until the certificate is replaced