The difficulty facing lewis and Clark was primarily

Ice, sleet and snow were additional burdens in the winter that brought the expedition to a halt for a number of weeks. The expedition also struggled with flooding in the spring. Flooding made it difficult to navigate the river and at least one time resulting in the capsizing of Lewis and Clark's boat. Nevertheless, Lewis and Clark's crew were plagued with illness, disease and accidents. A list of illnesses they suffered includes sunburn, dysentery, colds and flu. Dental problems and toothaches were also a problem. More serious illnesses and disease included small pox, cholera, venereal disease and pneumonia.

answer: i chose a.

explanation:

answer: the sentence in the text that contains both the topic and the author's single most important idea about the topic

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