Final answer:
J.C. Fremont's and Kit Carson's explorations played a key role in enhancing the understanding of North American geography, which was essential for subsequent westward migration and settlement.
Step-by-step explanation:
The explorations of J.C. Fremont and Kit Carson provided significant benefits to the understanding of North American geography. Their journeys aided in expanding the geographical knowledge of the West and contributed valuable information that supported further exploration, settlement, and westward migration. The correct answer to the student's question is C) Their explorations contributed to understanding North American geography.