Final answer:
Closure properties for decidable languages are used to prove a language is decidable by showing that operations like union, intersection, and complement on decidable languages result in a decidable language.
Step-by-step explanation:
To demonstrate that a language is decidable by a Turing machine, the best strategy would be to use Option C) Closure properties for decidable languages. Closure properties are rules that say if certain languages possess particular properties, then the combination (such as union, intersection, and complement) of those languages also possess those properties. In the context of decidable languages, these properties can show that if you start with languages known to be decidable, any language derived from them using these closure operations is also decidable.
For example, decidable languages are closed under union, intersection, and complement. That means if you have two decidable languages and you form a new language by taking the union, intersection, or complement of these two languages, the resulting language will also be decidable. This is crucial evidence when proving decidability, as you can combine simpler decidable languages in various ways to demonstrate that a more complex language is also decidable.