Refer to the exhibit.

According to theSD-WAN 7.6 Core Administratorstudy guide and theFortiOS 7.6 Administration Guide, the selection of a preferred member in aBest Quality (priority)rule is determined by the measured quality metric (latency, in this case) and thelink-cost-threshold.

Rule Logic (Best Quality): In the exhibit, the SD-WAN rule is configured with set mode priority, which corresponds to theBest Qualitystrategy. This strategy ranks members based on the link-cost-factor, which is set tolatency.

The Link-Cost-Threshold: The exhibit shows link-cost-threshold(10), which is the default 10% value. This threshold is designed to prevent "link flapping". To replace the current preferred member, a new member must not only have a better latency but must be better bymore than 10%.

The Calculation:

The current preferred member isHUB1-VPN1with a real latency of96.349 ms.

To calculate the "target" latency a lower-priority member must achieve to take over, we use the formula: $Target = \frac{Current\_Latency}{(1 + \frac{Threshold}{100})}$.

$\frac{96.349}{1.1} = \mathbf{87.59\text{ ms}}$.

Evaluating Options:

Option A (80 ms): Since 80 ms is lower than the required 87.59 ms target, HUB1-VPN3 successfully overcomes the 10% advantage of HUB1-VPN1 and becomes the new preferred member.

Option D (90 ms): While 90 ms is lower than 96.349 ms, it isnotlower than 87.59 ms. Therefore, the 10% threshold prevents a member switch, and HUB1-VPN1 remains preferred.

Option B: Incorrect because having a "lower" latency is not enough due to the 10% threshold.

Option C: If HUB1-VPN1 moved to 200 ms, HUB1-VPN2 (at 141.278 ms) would likely become the new preferred member before HUB1-VPN3 (at 190.984 ms).