Final answer:
It is true that closure properties can be used to show a language is decidable by a Turing machine, as applying operations like union or complement to decidable languages results in a decidable language.
Step-by-step explanation:
The statement that one could use closure properties to show that a language is decidable by a Turing machine is true. Closure properties are characteristics of certain language classes under certain operations.
For decidable languages, which are also known as recursively enumerable languages, if you perform operations such as union, intersection, concatenation, or complement on decidable languages, the resulting language is also decidable.
Knowing this, if you can construct a new language by applying these operations to languages already known to be decidable, then you can conclude the resulting language is decidable without directly constructing a Turing machine for it. This is a common technique in theoretical computer science for proving decidability.