Final answer:
Option (c), Hyperpigmentation is the condition where preventing further darkening of pigmented areas is a concern, unlike acne, eczema, or rosacea that have different symptoms and treatments.
Step-by-step explanation:
If you are trying to prevent further darkening of pigmented areas, then you are most likely treating hyperpigmentation. Hyperpigmentation is a condition where patches of skin become darker than the normal surrounding skin. This is due to an excess production of melanin, the brown pigment that produces normal skin color.
In contrast, acne is a skin condition characterized by the presence of pimples, blackheads, and sometimes cysts due to clogged pores infected with bacteria. Eczema is an inflammatory condition seen as a red, itchy skin rash. Rosacea is a chronic inflammatory skin condition resulting in redness, pimples, and visible blood vessels.