英语问答题When is your birthday party? A:When is your birthday party? B1:My birthday party is october 1st. B2:My birthday party is on october 1st. B1、B2哪个正确?还是都对? C:When is your birthday? D1:My birthday is June 4th. D2:My birthday is on June 4th. D1、D2哪个正确?还是都对?