Which statement best describes the behavior of a flow variable when a parent flow invokes a child flow via a flow reference?

• A. The variable is immutable
• B. The variable is accessible in the child flow and changes propagate back to the parent
• C. The variable is not visible to the child flow
• D. The variable is reset to null in the child flow

Answer: (B)

Flow variables represent per-message state that travels with the message as it moves through flows. When a parent flow calls a child flow with a flow reference, the same message, and thus the same flow variable map, is available to the child. If the child reads or writes a flow variable, those changes affect the same variable seen by the parent once control returns. That’s why the variable is accessible in the child and changes propagate back to the parent. It isn’t immutable, it isn’t hidden from the child, and it isn’t reset to null in the child.