Bicol arts festival
Passive: Various feasts and festival are observed by different religions.
Active: Different religions observe various feasts and festivals.
Passive: Christmas is considered the most joyous and elaborate festival by most Christians.
Active: Most Christians consider Christmas the most joyous and elaborate festival.
Passive: Easter is regarded by some Christian churches as their most important celebration.
Active: Christian churches regard Easter as their most important celebration.
Passive: Two big festivals are celebrated by flowers in Islam.
Active: Flowers celebrate two big festivals in Islam.
But this does not make sense. The original passive sentence could have been: Two big festivals are celebrated with flowers in Islam.
Active: They celebrate two big festivals with flowers in Islam.
Passive: The great festival is traditionally observed by Muslim at the end of the pilgrimages breaking of the festival.
Active: Muslim (singular verb in the original statement ) traditionally observes the great festival at the end of the pilgrimages breaking of the festival.