Gertrude and her husband planned a short desert hike on a hot summer day but have gotten lost. They find some shade trees to rest under and finish the small water bottle they brought. Which basic human need are Gertrude and her husband most likely at risk of missing?

Gertrude and her husband have run out of water while hiking in hot weather. Water is essential for hydration and is usually grouped with food as nourishment, a basic physiological need. They are not described as lacking air, love, or self-esteem.

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