1. 到底何時使用did？
did和其它助動詞一樣，本身無意義，自己不能獨(dú)立作謂語，只能和其它主要動詞一起構(gòu)成謂語，用于構(gòu)成一般過去時的否定句和疑問句，當(dāng)然也常常用于代替上文中的行為動詞的過去式。如:
I didn't go to school last Sunday. 上周日我沒上學(xué)。
Did you buy a new pen yesterday? 昨天你買了枝新鋼筆嗎？



2. did身后的動詞到底用什么形式？
有的小朋友總不注意did身后的動詞用什么形式，在否定句和疑問句中，
did身后的動詞必須用原形。  “他昨天沒有在家吃午飯?！?/span>
[誤] He didn't had lunch at home yesterday.
[正] He didn't have lunch at home yesterday.



3. 我能用be動詞代替嗎？
不管怎么說，含有行為(實(shí)義)動詞的一般過去時的肯定句變成否定句或疑問句時，不能用be動詞，必須用到did！含be動詞的句子構(gòu)成否定句或疑問句都絕不會讓did露面！  
例句：They went to the park last week. (改為否定句)
[誤] They weren't go to the park last week.
[正] They didn't go to the park last week.