Concept:
In calendar problems, Sundays occur at intervals of 7 days. Once the first Sunday is known, all subsequent Sundays can be determined by adding 7 repeatedly.
Step 1: Analyze Statement I alone.
First Sunday is on 5th. So Sundays are:
\[
5,\ 12,\ 19,\ 26
\]
March has 31 days, so the last Sunday is 26th.
Statement I alone is sufficient.
Step 2: Analyze Statement II alone.
Given last day is not Saturday, but this does not fix the Sundays or their dates uniquely.
Statement II alone is NOT sufficient.
Step 3: Combine both statements.
Since Statement I alone already gives a unique answer, combining is unnecessary.
Hence, Statement I alone is sufficient.