Which of the following is a sign of skin aging?

Fine lines and wrinkles are indeed a prominent sign of skin aging. As skin ages, it undergoes various changes due to a combination of intrinsic factors like genetics and extrinsic factors such as sun exposure and lifestyle choices. Over time, the skin loses collagen and elastin, leading to a decrease in firmness and elasticity. This loss manifests as fine lines and wrinkles, which often first appear around the eyes and mouth. Additionally, the skin's ability to retain moisture diminishes, contributing to a more pronounced appearance of lines and texture changes, making fine lines and wrinkles a clear indicator of aging.

In contrast, increased elasticity, lower oil production, and reduced pigmentation do not directly align with the typical signs of skin aging in the way fine lines and wrinkles do. While these factors may accompany skin aging, they do not signify aging as prominently or clearly as the presence of fine lines and wrinkles.