The triplet code can produce 64 possible codon combinations. what is an advantage of this

The main answer wold be diversity.

When you think about it, you only have a triplet code (which requires much less physical space than having all 64 possible codon combinations already present but either turned off or on). It makes much sense to have less actual physical compounds which can be combined in different ways (and a lot of ways) and produce the variety that can be required. 

Ribonuclease activity is a type of nuclease that catalyzes the degradation of rna into small components.