How does creating a new default merge policy affect segments within a sandbox?

Creating a new default merge policy in a sandbox directly impacts the segments within that environment by leading to potential changes in their membership. When a new default merge policy is established, any segments that were previously defined may need to be re-evaluated against the new criteria dictated by this policy. This reassessment can affect which data points are included in those segments, ultimately influencing the membership of the segments.

Segments are fundamentally linked to the merge policy, as this determines how profiles are combined and what attributes are considered during segmentation. Consequently, when the merge policy changes, segments will adapt according to the new parameters, potentially altering who is included in a segment based on the updated rules.

The other options reflect scenarios that do not accurately capture the dynamic between merge policies and segments. Segments are not left unchanged; they will adapt to new policies which may enhance or restrict their membership. While it is true that a sandbox can have multiple merge policies, only one is designated as the default at a time. The notion that segments would be permanently deleted does not align with how merge policies function, as they alter membership but do not remove segments altogether.