To solve this question, the user needs to have knowledge of programming concepts and the purpose of sub procedures.

A sub procedure, also known as a subroutine or function, is a block of code that performs a specific task or set of tasks within a larger program. It is called by the main program and helps in organizing and modularizing the code.

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

A. makes code easier to maintain: This option is correct. By using sub procedures, the code is divided into smaller units, making it easier to understand, debug, and maintain. Changes or updates can be made to a specific sub procedure without affecting the entire code.

B. splits the logic to solve a problem into small, manageable units: This option is correct. Sub procedures help in breaking down complex problems into smaller, more manageable tasks. Each sub procedure focuses on solving a specific part of the problem, making the overall logic easier to understand and implement.

C. limits the number of times the code can be accessed: This option is incorrect. Sub procedures do not limit the number of times the code can be accessed. They can be called multiple times from different parts of the program as needed.

D. Both a and b: This option is correct. Both options A and B are correct, as explained above. Sub procedures make code easier to maintain and split the logic into small, manageable units.

E. All of the above: This option is incorrect. Option C is incorrect because it does not accurately describe the purpose or benefit of sub procedures. Sub procedures do not limit the number of times the code can be accessed.

Therefore, the correct answer is:

D. Both a and b.