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A
To cleanse
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B
To hydrate and protect the skin after treatment (sun protection guards against UV damage)
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C
To exfoliate
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D
To cut the skin
Why this is the answer
Moisturizer, and often sun protection, is commonly the final step of a facial to hydrate the freshly treated skin and protect it — sunscreen in particular guards against UV damage, which is especially relevant because some facial treatments can leave skin more sensitive to the sun. Finishing with appropriate protection supports skin health and the results of the service. Recommending sun protection also educates the client. Knowing why a facial ends with moisturizing/protection is part of the facial-sequence knowledge on the exam.
Source: Skin & Nails — Moisturize and Protect