根据要求改写句子和填空。
1. We had a maths exam yesterday. (对划线部分提问)
_____ _____ you _____ yesterday?
2. I want to get another piece of cake. (保持原意，改写句子)
I _____ ______ to _____ _____ _____ piece of cake.
3. The snow was very heavy yesterday. (改为同义句)
_____ _____ very _____ yesterday.
4. He'll buy some school things tomorrow. (改为否定句)
He ______ ______ ______ school things tomorrow.
