Software reuse is

Answer: Software reuse is the process of using existing software artifacts and knowledge to build new software.

Why this is correct:

• Using libraries, frameworks, components, design patterns, or prior designs to save development effort and reduce defects.

• Reusing knowledge (best practices, documentation, test cases) to speed development and improve quality.

Why the other choices are incorrect:

• The description 'the process of analysing software with the objective of recovering its design and specification' refers to reverse engineering — understanding and extracting designs from existing code — not to reusing artifacts to build new systems.

• The description 'concerned with reimplementing legacy system to make them more maintainable' refers to software reengineering or migration, which focuses on modernizing systems rather than the general practice of reusing existing artifacts to create new software.

• The description 'analysing software to create a representation of a higher level of abstraction and breaking software down into its parts to see how it works' describes program comprehension or reverse engineering for understanding, not the act of reusing artifacts to build new software.

Practical note: Reuse can occur at many levels (code snippets, classes, modules, services, architectures). Effective reuse requires good documentation, modular design, and awareness of licensing and compatibility.