睁大眼睛，根据提示，猜猜这4张图都是什么？

睁大眼睛，根据提示，猜猜这4张图都是什么？

Its an animal. It has a thick shell（壳） on its back. It crawls（爬） very slowly.

It is a juicy（多汁的） fruit. It looks like a heart. We usually eat them in summer.

It is a card. People use it to send messages（發送信息） by post.

It is a room. Schools have many. Teachers and students have classes in it.