Explanation:

Assembly language is a low-level programming language that uses symbolic code (mnemonics) to represent machine code instructions. To execute an assembly language program, it must first be translated into binary machine code. This specific translation is performed by an **assembler**. A 'compiler' (option b) translates high-level languages (like C++, Java) into machine code, while an 'interpreter' (option c) translates and executes high-level code line by line. A 'processor' (option d) is the hardware component that executes instructions, not the software that translates them. Therefore, the assembler is the dedicated program for converting assembly language into machine language.