Which of the following is an example of a mild skin tonic?

Rosewater is indeed considered a mild skin tonic due to its soothing properties and gentle nature. It is often used to hydrate and refresh the skin, making it ideal for sensitive or irritated skin types. Rosewater is derived from the steam distillation of rose petals, which imparts its calming aroma and skin benefits without harsh effects. It helps maintain the skin's pH balance, reduces redness, and provides a light, natural fragrance.

In contrast, the other options serve different purposes. Witch hazel is more of an astringent with a stronger effect, often used to tighten skin and reduce inflammation but can be drying for some skin types. Tea tree oil is known for its antiseptic and antibacterial properties, making it more suitable for oily or acne-prone skin, though it can be irritating if not diluted properly. Salicylic acid is a potent beta hydroxy acid primarily used to exfoliate and treat acne, making it much stronger than a mild tonic and potentially irritating for sensitive skin. Therefore, rosewater stands out as the gentlest and most suitable option for a mild skin tonic.