猜謎是一種很好的鍛煉思維的方式。同學(xué)們，快叫上你的爸爸媽媽或好朋友，大家一起來猜謎語，看誰先猜出來哦！

1. What are full when they are used（使用） and empty when they are at rest（休息）？

2. What always has one eye open but cant see？

Hint：They protect（保護） your feet from being hurt（受傷）.

Hint：It is made of（由……制成） metal（金屬）.

3. We see it once in a year， twice in a week， and never in a day. What is it？

4. What gets larger， the more you take away（拿走）？

Hint：A letter.

Hint：Some animals live there.