Do they did there homework last weekend?中“did” 为什么换成do 不是助动词后面跟动词原形的吗

Do they did there homework last weekend?中“did” 为什么换成do 不是助动词后面跟动词原形的吗 What did they do yesterday? what did they do next? what did they do finally? what did they do first? What did you do there what()they()they()there?what()they()they()there?[do] How did they get there?意思 what will they do there? How do they go there? how do they go there? What did they do last weekend?They_____sports what did they do outside中文解释 What did they do at the weekend? What did they do then怎么回答 What did you do there?写出意思 What did you do there?怎么回答 What did they do after havingWhat did they do after having dinner?