Computational complexity theory:

However, some computational problems are easier to analyze in terms of more unusual resources. For example, a non-deterministic Turing machine is a computational model that is allowed to branch out to check many different possibilities at once. The non-deterministic Turing machine has very little to do with how we physically want to compute algorithms, but its branching exactly captures many of the mathematical models we want to analyze, so that non-deterministic time is a very important resource in analyzing computational problems.

Please answer a question about this article. If the question is unanswerable, say "unanswerable". What is the least critical resource in the analysis of computational problems associated with non-deterministic Turing machines?
unanswerable