The design concept 'Refinement' is a:

Explanation

Stepwise refinement, introduced by Wirth, is a top-down design strategy in which a statement of function is successively decomposed until it is expressed in the primitives of the programming language, so option 1 is true. Pressman explicitly calls refinement the complement of abstraction: abstraction suppresses low-level detail while refinement reveals it, and the two work together as a designer moves down the levels. Because each refinement step elaborates the previous one by adding detail, it is also correctly described as a process of elaboration. All three descriptions hold, so the answer is all of the above.