Which of the following is true about an interpreter?

The statement that an interpreter translates source code line by line is true. An interpreter processes code incrementally, executing one line at a time. This approach allows for immediate execution of the code, enabling developers to see results instantly. This can be particularly useful during the development process, as it facilitates easier debugging and allows for interactive coding environments where changes can be tested on the fly.

The other options do not accurately describe the behavior of an interpreter. The first option describes a compiler's functionality, which translates the entire source code into machine code before executing it. The third option is misleading, as interpreters generally run code in the foreground; their operation is not limited to background execution. Lastly, the fourth option is incorrect because interpreters do not require the code to be fully debugged beforehand; they allow for real-time testing and debugging as the code is executed line by line.