The correct answer to this open question is the following.
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The explanatory variable in this informal study is Herbal tea.
Herbal tea is the variable because it is the element that makes the affirmations possible. Herbal tea is the factor that has improved the conditions and moods of people who live at the nursing home. Nurses have noted that people have a better semblance. And although this fact cannot be proved scientifically, it has provoked a positive reaction in patients.