Which characteristic specifically describes interpreted languages?

The characteristic that specifically describes interpreted languages is that they can be run on any machine having the right interpreter. This means that unlike compiled languages, which are translated into machine code specific to a particular operating system or hardware architecture before execution, interpreted languages are processed at runtime by an interpreter. This allows the same code to run on different platforms as long as there is a compatible interpreter available.

The flexibility provided by this characteristic enhances portability because the source code can remain unchanged while allowing it to be executed on various systems. As a result, developers can write their code once and leverage the interpreter's capabilities to run it in diverse environments, making interpreted languages highly adaptable for different operating systems.

The other options do not accurately reflect the nature of interpreted languages. For instance, not all interpreted languages execute code in parallel threads, nor do they generally outperform compiled languages in speed, which is a common trait of compiled languages due to the direct translation of code to machine language before execution. Moreover, the claim that they compile code ahead of time does not apply, as interpretation does not involve pre-compilation into machine code.