Quiz: Sorting Applications

To arrange numbers like $[3, 30, 34, 5, 9]$ into the largest possible number "9534330", what determines the sort order?

1. A.Sort by numeric value in descending order
2. B.Compare concatenations: $a+b$ vs $b+a$ as strings
3. C.Sort by string length, shortest first
4. D.Sort by first digit, then by length