1. What did you do during the summer vacation?

Question

2. What did you do during summer vacation?

(Which one is correct, #1 or #2?)

Answer 1

Both are correct, but # 2 is used more often.

Answer 2

Thank you?
What about the following?

1. on (the) summer vacation.
2. over (the) summer vacation

(Are both all correct?)

Answer 3

Grammatically, all are correct, but with the word "the" included, the sentences would read awkwardly. Better to omit "the."