3 . 选择合适短语并用其适当形式填空，其中一项为多余选项。

stand for；convert... into；pay off in exchange for；a variety of；combine...with

1. To stay healthy, we need to eat ________ foods.
2. Tom gave me a lift ________ a delicious meal.
3. They ________ the spare bedroom ________ an office.
4. People often ________ eating ________ the company of friends and family because both experiences are pleasurable.
5. In the food pyramid, each color ________ a food group.

4 . 50,000 square kilometers of rice fields were _________(改变) to growing vegetables and other cash crops. (根据汉语提示单词拼写)