Assembler Features that are Machine-Dependent

Assembler is a low-level programming language that converts the source code written in assembly language to machine language. Assembler language is specific to a particular computer architecture and operating system. Therefore, certain features of assembler are machine-dependent. These features are:

1. Instruction Formats
The instruction format in assembler depends on the computer architecture. Different computer architectures have different instruction formats. For instance, the instruction format for Intel x86 processors is different from the instruction format for ARM processors. Assembler language must be written according to the instruction format of the target processor.

2. Addressing Modes
Addressing modes in assembler are also machine-dependent. Addressing modes specify how a memory location is accessed by an instruction. Different processors have different addressing modes. For example, the Intel x86 processor has addressing modes such as direct addressing, indirect addressing, indexed addressing, etc. On the other hand, ARM processors have addressing modes such as immediate addressing, indirect addressing, etc. Assembler language must be written according to the addressing modes of the target processor.

3. Program Relocation
Program relocation is the process of modifying the program code to run at a different memory location. The process of program relocation is machine-dependent. Different processors have different memory layouts and relocation schemes. Assembler language must be written according to the relocation scheme of the target processor.

4. All of the Mentioned
All of the above-mentioned features of assembler are machine-dependent. Assembler language must be written according to the instruction format, addressing modes, and program relocation scheme of the target processor. Therefore, the correct answer is option 'D'.