The main role of the liver in the digestive system includes several functions, but specifically concerning digestion, its primary roles are to produce bile and to store and concentrate bile, which is essential for the digestion and absorption of fats. The liver also processes nutrients absorbed from the digestive tract but is not primarily involved in urine production, which is the function of the kidneys.
Considering the options you've provided, the best answer would be:
To produce bile.
However, if you're looking for an answer that encompasses all roles mentioned, you might consider All of the above since the liver does contribute to waste removal and other processes, even though those are not its primary functions in digestion.