user: Question: Which Barrel twist has a Stock of Canadian 3rd Generation and a Hand guards of Short Ribbed?
Columns: ['Colt model no.', 'Diemaco model', 'Stock', 'Fire control', 'Rear sight', 'Forward assist', 'Barrel length', 'Barrel profile', 'Barrel twist', 'Hand guards', 'Bayonet Lug', 'Muzzle device']
Types: ['text', 'text', 'text', 'text', 'text', 'text', 'text', 'text', 'text', 'text', 'text', 'text']
Sample row: ['715', 'C7', 'A2', 'S-1-F', 'A1', 'Yes', '20 in.', 'A2', '1:7', 'Ribbed', 'Yes', 'A2']
SQL:

assistant: SELECT "Barrel twist" FROM "Table" WHERE "Stock" = 'Canadian 3rd Generation' AND "Hand guards" = 'Short Ribbed';