CAPM Practice: Determine how to gather requirements

Reverse engineering an existing system — studying its inputs, outputs, and behavior — can recover implicit requirements when original documentation is lost. It's especially useful for legacy system modernization projects.

**Why not A:** Rebuilding a failed system from scratch using newer technology is a system replacement or modernization strategy, not a requirements technique. Reverse engineering specifically focuses on studying what an existing system already does in order to extract its implicit requirements — rebuilding from scratch would come after that analysis, not instead of it.

**Why not B:** Machine learning tools that generate requirements from user data represent a category of automated requirements discovery, but this is not what "reverse engineering" means in BA practice. Reverse engineering is a manual, human-led process of analyzing observable system behavior to deduce underlying requirements, and the term predates machine learning by decades.

**Why not D:** Examining competitor products for intelligence or inspiration is called competitive analysis or benchmarking, not reverse engineering in the BA context. As a BA requirements technique, reverse engineering refers specifically to recovering requirements from an existing system you own or are responsible for — not to competitive intelligence gathering.