平行,因为CO'D是COD对折过来的,
所以∠CO'D=∠COD,
又O'D平行AC,
所以∠ACO'=∠CO'D,
∠ACO'=∠CO'D与∠CO'D=∠COD推出∠ACO'=∠CO'D,
那么根据角、边、角原理推出O'D平行AC