With Least Connections (member), BIG-IP attempts to send new connections to the pool member with the fewest current connections. In a perfectly ''stateless'' scenario (no affinity), this often trends toward a fairly even distribution over time.

However, persistence overrides load balancing:

When a persistence profile is applied, BIG-IP will continue sending a client (or client group) to the same pool member based on the persistence record (cookie / source address / SSL session ID, etc.).

This means even if another pool member has fewer connections, BIG-IP may still select the persisted member to honor session affinity.

The result can be uneven active connection counts, even though the configured load balancing method is Least Connections.

Why the other options are not the best cause:

A . Priority Group Activation is disabled

Priority Group Activation only affects selection when priority groups are configured; disabling it does not inherently create uneven distribution under Least Connections.

B . SSL Profile Server is applied

A server-side SSL profile affects encryption to pool members, but it does not by itself cause skewed selection across pool members. (Skew could happen indirectly if members have different performance/latency, but that's not the primary, expected exam answer.)

D . Incorrect load balancing method

Least Connections is a valid method and does not itself explain unevenness unless something is overriding it (like persistence) or pool members are not all eligible.

Conclusion:

A persistence profile is the most common and expected reason that active connections become unevenly distributed, because persistence takes precedence over the Least Connections load-balancing decision.