Step 1: Analyze Statement I:
- This tells us that yesterday was not Monday.
- However, this does not give us any definite information about whether tomorrow is Sunday.
Conclusion: Statement I alone is insufficient.
Step 2: Analyze Statement II:
- This tells us that the day before yesterday was not Thursday.
- From this, we can determine that yesterday was not Friday and today is not Saturday.
- If today is not Saturday, then tomorrow must be Sunday.
Conclusion: Statement II alone is sufficient to answer the question.