The most likely reason from the options provided is b. the distance makes it difficult to get there.
Both Canada and Australia are geographically far from Syria, and the journey can be challenging and costly for refugees. While these countries have had programs to welcome Syrian refugees and have expressed a commitment to helping them, the logistical barriers of distance, travel costs, and obtaining visas can significantly impact the number of refugees who are able to reach these countries.
The other options provided do not accurately reflect the situation regarding Syrian refugees and their relocation to these countries.