What does the term 'threshold dose' relate to?

The term 'threshold dose' refers to the minimum amount of a substance or exposure that is necessary to produce a detectable effect. This means that below this specific dose, no response or measurable effect can be observed in the biological system. Understanding the concept of threshold dose is crucial in toxicology and pharmacology, as it helps in determining safe levels of exposure to substances, whether they are drugs, chemicals, or environmental toxins. Therefore, option B accurately captures this definition, highlighting the significance of identifying a starting point for responsiveness in biological systems.