Final answer:
A sprint is a pre-specified, fixed period of time in agile development during which a team works at a sustainable pace to complete a selected set of work items from the product backlog.
Step-by-step explanation:
The best description for a sprint is option a: A sprint is a pre-specified amount of time in which the development team works at a sustain pace to complete a chosen set of work. This definition aligns with the agile methodology practices where a sprint is typically a two to four-week period where the development team works to complete items from the product backlog, which have been prioritized and agreed upon for that sprint during the sprint planning meeting. It is not about working as many hours needed but rather working effectively within the set time frame.