Explanation:

Assembly language is a 'low-level programming language'. It is a symbolic representation of machine code, using mnemonics (e.g., `ADD`, `MOV`, `JMP`) to represent machine instructions. While it is more human-readable than raw binary machine code, it is still very close to the computer's hardware architecture and requires an assembler to translate it into machine code. Option (a) 'high level programming language' is incorrect, as high-level languages are much more abstract. Option (c) 'machine language' is also incorrect; assembly language is a symbolic representation *of* machine language, not machine language itself. Machine language is the raw binary instructions directly executed by the CPU. Therefore, assembly language occupies the tier just above machine language, making it a low-level programming language.