單字：

cowboy (牛仔), earring (耳環), mailbox (郵箱), football (足球), goldfish (金魚), 

snowman (雪人), homework (功課), backyard (後院), airplane (飛機), sunhat (太陽帽)。

句子：

1. What is a compound word ? (Two words put together make a new word.）
2. A board to skate on is a __________ ? (skateboard.）
3. A house for a bird is a __________ ? (birdhouse.)