What characteristic defines machine/low-level language?

Machine language, also known as low-level language, is characterized by its direct correspondence with a computer's hardware architecture. This language consists of binary code that the computer's processor can execute directly. It is designed specifically for a particular type of machine, meaning each type of CPU has its own unique machine code.

One of the critical traits of machine language is that it operates independently of an operating system. Unlike higher-level programming languages, which rely on compilers, interpreters, or a specific OS to function, machine language is executed directly by the hardware. This allows for maximum efficiency and performance but comes at the cost of being difficult to read and write for humans. The other choices do not accurately reflect the nature of machine language; it is neither user-friendly nor object-oriented, and while it can run on systems without a traditional OS, it is designed for the specific machine architecture it operates on.