Please answer the following question: I want to test the ability of students to read a passage and answer questions about it. Could you please come up with a good question for the passage "Wood has been an important construction material since humans began building shelters, houses and boats. Nearly all boats were made out of wood until the late 19th century, and wood remains in common use today in boat construction. Elm in particular was used for this purpose as it resisted decay as long as it was kept wet (it also served for water pipe before the advent of more modern plumbing)."?
A:
Wood is often used for building houses, boats and?