Which of the following best describes toxic substances?

Toxic substances are best described as agents that can cause harm to living cells. This harm can manifest in various ways, including disrupting cellular processes, damaging DNA, or leading to cell death. Understanding this definition is essential in fields such as nanotechnology and toxicology, as it highlights the potential dangers of materials and chemicals that may be used or encountered.

Options that suggest toxic substances enhance cell growth, are necessary for life, or promote healing misinterpret the nature of toxicity. While some substances are essential for health and may have beneficial effects in certain contexts, toxic substances specifically refer to those that pose risks and can lead to adverse effects on health and well-being. Therefore, the accurate understanding of toxic substances focuses on their harmful potential, firmly establishing the correctness of the chosen answer.