To solve the question, the user needs to know about the Zero flag and the SUB instruction in assembly language.

The Zero flag is a status flag in the processor's flag register that indicates whether the result of an arithmetic or logical operation is zero. When a program performs a subtraction operation, the Zero flag is set if the result of the operation is zero, and it is cleared otherwise.

The SUB instruction is used for subtraction operations in assembly language. In the instruction SUB AX, AX, the value of register AX is subtracted from itself, resulting in a zero value.

Now, let's go through each option and explain why it is right or wrong:

A. Set: This option is correct. Since the result of the SUB AX, AX operation is zero, the Zero flag is set.

B. Cleared: This option is incorrect. The Zero flag is set because the result of the SUB AX, AX operation is zero.

C. Unknown: This option is incorrect. The Zero flag is set because the result of the SUB AX, AX operation is zero.

D. None of the above: This option is incorrect because option A is the correct answer.

Therefore, The Answer is: A. Set

To determine which instruction(s) can be performed only in the CX register, we need to understand the purpose and limitations of the CX register.

The CX register is a 16-bit general-purpose register in the x86 architecture. It is commonly used as a loop counter in assembly language programming. The CX register can be modified by instructions such as LOOP and is used for controlling the number of iterations in a loop.

Now let's go through each option and explain why it is right or wrong:

A. LOOP: This option is correct. The LOOP instruction is used to create a loop in assembly language programming. It decrements the CX register by 1 and jumps to the specified label as long as the CX register is not zero. The LOOP instruction relies on the CX register and is commonly used for iterative operations.

B. MUL, DIV, CBW: This option is incorrect. The MUL (multiply), DIV (divide), and CBW (convert byte to word) instructions do not specifically depend on the CX register. These instructions can work with other registers, such as AX, DX, and AL, based on the requirements of the specific instruction. They are not exclusive to the CX register.

C. ADD, SUB: This option is incorrect. The ADD (addition) and SUB (subtraction) instructions do not depend on any specific register. They can be used with various registers, including the CX register, based on the instructions' requirements. They are not limited to the CX register.

D. none of the above: This option is incorrect. As explained above, the LOOP instruction can only be performed in the CX register. Therefore, option A is the correct answer.

The answer is: A. LOOP

To solve this question, the user needs to have knowledge of assembly language programming and the purpose of assembly directives.

Assembly directives are commands or instructions in assembly language that are used to provide information to the assembler program. These directives are not executed by the microprocessor, but they instruct the assembler on how to process the assembly code.

Now, let's go through each option and explain why it is right or wrong:

A. The Assembler program: This option is correct. Assembly directives are commands to the assembler program, telling it how to process the assembly code. The assembler program reads the assembly code, processes the directives, and generates the corresponding machine code.

B. The Microprocessor: This option is incorrect. Assembly directives are not commands to the microprocessor. The microprocessor executes machine code, not assembly code. Assembly directives are used by the assembler program to generate the appropriate machine code.

Therefore, the correct answer is:

The Answer is: A

To answer this question, the user needs to have knowledge of the 8086 processor and its limitations.

Now, let's go through each option and explain why it is right or wrong:

A. It has only 14 registers: This option is incorrect. The number of registers in the 8086 processor does not determine the maximum memory space addressable. The registers in the 8086 are used for various purposes, but they do not directly limit the addressable memory space.

B. The register size was 16 bits: This option is incorrect. The size of the registers in the 8086 processor does not directly determine the maximum memory space addressable. The register size affects the size of the data that can be stored and manipulated within the registers, but it does not limit the overall addressable memory space.

C. The address bus width was 20 bits: This option is correct. The address bus width of the 8086 processor is 20 bits, which means it can address up to 2^20 (1,048,576) memory locations. Each memory location can hold a byte of data. Therefore, the 8086 processor can address a maximum of 1,048,576 bytes or 1 megabyte of memory.

D. none of the above: This option is incorrect. Option C, which states that the address bus width was 20 bits, is the correct answer.

The Answer is: C