Question

As Kiev increased its trade and contacts around the region, the most significant result was that

Answer 1

Since you provide no options,

The most significant result probably that Kiev was able to increase its wealth

After Kiev increased its trade around that region , they're able to buy more manpower and equipments that would help them in their cause

Answer 2

As Kiev increased its trade and contacts around the region, the most significant result was that

Kiev became the center of cultural exchange.