What is causing these complaints?

Universal Containers is currently doing User Acceptance Testing for small changes in a Developer sandbox. Users are complaining that allow release to production, some functionality is broken and performance is often negatively impacted.

What is causing these complaints?
A . Users should be testing in a Partial Sandbox in order to replicate Production functionality and performance characteristics.
B . Users should be testing in a Full Sandbox in order to replicate Production functionality and performance characteristics.
C . Users should be testing with date loaded into the Developer sandbox in order to replication Production functionality and performance, characteristics.
D . Users should be testing in a Developer Pro sandbox in order to replicate Production functionality and performance characteristics.

Answer: B