Tom doesn't do morning exercise.He cooked food at home yesterday.(改为否定句）He didn't cook food at home yesterday.因为cooked是过去式，所以回答是要用didn't 吧？是的，一定要注意时态，另外，第一题中的does 是实义动词，变否定句时要加助动词doesn‘t ，原来的动词does 要用原形，即do谢谢你啊，感谢感谢如果满意，请采纳，谢向！