Based on the context and the answer, generate a question. 

Context: Alcohol just never seemed to be an intoxicating substance for him . He could drink extensively , the strongest liquor available ( and in fact his chosen beverage was Absinthe ) , but still remain completely sober . Marijuana acted much like an energy drink would to someone else .

Answer:

They are used to drinking a lot of alcohol .



Why is their friend able to drink so much ?