Volume will represent a continuous data set.
Why? because you can have any measurement (1 oz, 0.1 oz, 0.001 oz, etc)
A discrete data set is when you cannot have a "part" of the whole. An example would be if the data set is the number of people ... you can't have 1/2 of a person. Another example would be a product (tv, laptop, etc) ... you can't have a part of the product. you either have 1 or 2 or 3, etc.
Answer: Continuous