This task is about creating an unanswerable question based on a given passage. Construct a question that looks relevant to the given context but is unanswerable. Following are a few suggestions about how to create unanswerable questions:
(i) create questions which require satisfying a constraint that is not mentioned in the passage
(ii) create questions which require information beyond what is provided in the passage in order to answer
(iii) replace an existing entity, number, date mentioned in the passage with other entity, number, date and use it in the question
(iv) create a question which is answerable from the passage and then replace one or two words by their antonyms or insert/remove negation words to make it unanswerable.

Q: Passage: Even though some proofs of complexity-theoretic theorems regularly assume some concrete choice of input encoding, one tries to keep the discussion abstract enough to be independent of the choice of encoding. This can be achieved by ensuring that different representations can be transformed into each other efficiently.

A: What can not be achieved by ensuring different representations can transformed into each other efficiently?
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Q: Passage: The innovative production techniques devised by post-punk producers such as Martin Hannett and Dennis Bovell during this period would become an important element of the emerging music, with studio experimentation taking a central role. A variety of groups that predated punk, such as Cabaret Voltaire and Throbbing Gristle, experimented with crude production techniques and electronic instruments in tandem with performance art methods and influence from transgressive literature, ultimately helping to pioneer industrial music. Throbbing Gristle's independent label Industrial Records would become a hub for this scene and provide it with its namesake.

A: Who avoided post-punk production?
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Q: Passage: In the context of relativity, mass is not an additive quantity, in the sense that one can add the rest masses of particles in a system to get the total rest mass of the system. Thus, in relativity usually a more general view is that it is not the sum of rest masses, but the energy–momentum tensor that quantifies the amount of matter. This tensor gives the rest mass for the entire system. "Matter" therefore is sometimes considered as anything that contributes to the energy–momentum of a system, that is, anything that is not purely gravity. This view is commonly held in fields that deal with general relativity such as cosmology. In this view, light and other massless particles and fields are part of matter.

A:
What type of quantity is mass?
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