单语范例（未经PONS编辑处理）
This program is designed to view trees of all sizes and is very useful for creating figures.
en.wikipedia.org He was responsible for the giving of useful advice and information that helped to end that problem.
en.wikipedia.org It stands on 84 square meters and nets 312 square meters of useful space.
en.wikipedia.org The short, rounded wings provide good initial lift and are useful for short flights, though not for extended jaunts.
en.wikipedia.org The restraining bar is also useful in very strong wind and when the chair is coated by ice.
en.wikipedia.org