I don't think there are such threads as (2 Edges)
 1 2
 2 1

And although my program can solve that case, I still WA on test5. Can you help me and give me some advice? Thank you very much!

Use union+Rank can AC....

Use union+Rank can AC....

Try this test:
4 4
1 2
1 2
2 3
3 4
3
1 2 3
Answer 1 2 3