Q:

Split content of a column and get the other replicated

I have a file (too large) with a structure like this
A B C,D,E,F

The third column contains 4 values (but could be variable) separated with commas. I would like to convert that file into 
A B C
A B D
A B E
A B F

Basically replicating the first two and splitting the second into rows.
Any idea on how to do that in awk?

A:

$ awk '{n=split($3,a,/,/);for(i=1;i<=n;i++)print $1,$2,a[i]}' file
A B C
A B D
A B E
A B F

