Read and Complete

Choose the word that best completes each blank.

Venice was built on soft mud in a shallow lagoon, so its builders could not lay ordinary foundations. Instead, they drove millions of wooden poles deep into the mud until they reached firmer ground. Buildings were then constructed on top of these poles. Cut off from oxygen under the water and mud, the wood did not rot but slowly hardened over the centuries, helping to support the famous city above.

The builders of Venice supported their city by driving wooden —polesstonesropes into the mud, and because the wood was cut off from —oxygensunlightsalt, it did not —rotfloatburn but grew harder over time.