Final answer:
Arab merchants played a crucial role in spreading Islam to various regions, except northern Asia.
Step-by-step explanation:
Arab merchants played a crucial role in spreading Islam across various regions. They carried out trade expeditions to different parts of the world and introduced Islam to new regions. They were particularly instrumental in spreading Islam to India, Africa, and Southeast Asia.
However, northern Asia, which includes regions such as Siberia, Mongolia, and China, did not experience significant Arab merchant activities that led to the widespread propagation of Islam.
Therefore, the correct answer is b. northern Asia, as Arab merchants did not play a significant role in spreading Islam to this region.
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