Answer: Option (B) is correct.
Step-by-step explanation:
From the given comprehension it can be stated the following would it be most useful to know in order to assess the argument "big-budget films will lead to the eventual demise of art-house cinema." : The demand for art-house films will be substantially lower than blockbusters.
Therefore, if the demand for art-house films will be considerably lower than that for blockbusters, then we can conclude that big-budget films will lead to the eventual demise of art-house cinema.