Final answer:
The best techniques for representing user task descriptions are user stories, scenarios, and use case specifications because they provide a detailed narrative view of user interactions with the system.
Step-by-step explanation:
The most appropriate techniques for showing, analyzing, or discovering user task descriptions are User stories, scenarios, and use case specifications. These techniques allow for a narrative explanation of what a user wants to achieve with a system and the process they will follow to complete tasks. User stories provide a simple description of a software feature from an end-user perspective. Scenarios and use cases give a detailed account of how the system is used, often highlighting various conditions and outcomes.
Meanwhile, techniques like state-transition diagrams and state tables are more suitable for showing system behavior in response to events or conditions, whereas detailed screen layouts and high-fidelity prototypes demonstrate the look and feel of the end product. Entity-relationship diagrams are used to model data systems but are not directly focused on user tasks.