In any number system the digits **cann't be greater** than its **Radix**

Eg; If we consider Radix-2 that is Binary number system we can have 0-1 but not 2

Same way in Radix-3 all the numbers should be less than 3 i,e; 0,1,2 but 3 is not possible

**This another blunder from ACE tests i guess**