Which of the following best describes nits associated with lice infestations?

Nits, or the eggs of lice, are best described as being firmly attached to the hair shaft, which helps distinguish them from other types of debris. They are typically found close to the scalp where the warmth promotes hatching. Although nits can often appear empty because the lice have already hatched, their firm attachment to the hair is a distinctive characteristic.

The attachment method is crucial because nits that are loosely held or free to fall are not likely to be viable, as they would not survive the environmental exposure or fall off before hatching. This firmly attached characteristic indicates that the nits are in the process of developing, making option D the most accurate description among the choices provided. In addition, the color of nits can vary from white to yellowish but the key factor remains their attachment to the hair strand.