"hard" 作为副词时，表示“努力地、费力地、艰难地、猛力地、猛烈地、彻底认真地”。以下是一些使用 "hard" 的例句：

1. She has been working hard all day to finish the project on time.

2. They tried hard to overcome the obstacles in their path.

3. It was hard to breathe in the smoky room.

4. He fell off the bike and hurt himself, but he continued to ride hard afterwards.

5. They fought hard in the final match to secure victory.

希望这些例句能帮助你理解 "hard" 作为副词时的用法。