Which of the following statements is correct about the metal-bound arene ring in    (η6-C6H6)Cr(CO)3?

a- The metal-bound ring is more susceptible to attack by electrophiles than free C6H6

b- The metal-bound ring is more susceptible to attack by nucleophiles than free C6H6

c- The metal-bound ring readily undergoes addition reactions, whereas free C6H6 does not

d- The metal-bound ring is less susceptible to attack by nucleophiles than free C6H6