How much work must a Development Team do to a Product Backlog item it selects for a Sprint?

How much work must a Development Team do to a Product Backlog item it selects for a Sprint?
A . A proportional amount of time on analysis, design, programming, testing, and documentation.
B . As much as it can fit into the Sprint. Any remaining work will be transferred to a subsequent Sprint.
C . All development work and at least some testing.
D . As much as it has told the Product Owner will be done for every Product Backlog item it selects in conformance with the definition of “Done”.

Answer: D