Threshold  quantity is:

Correct option is D

The Threshold is the point or limit at which an effect or change becomes noticeable. In this case, threshold refers to the maximum limit at which a toxic effect does not occur. It is the highest level of exposure to a substance (such as a chemical or radiation) at which there is no observable adverse effect. Beyond this limit, harmful effects start to manifest.

Information Booster:

1. Threshold is essentially the maximum level at which an effect is absent, and any further increase in exposure will cause a toxic effect.

2. This concept is widely used in toxicology, medicine, and environmental science, where it helps to identify the safe exposure limits to various substances.

3. Threshold values help in determining how much of a substance can be safely absorbed or exposed to without triggering harmful consequences.

4. If exposure stays below the threshold, the toxic effects will not be visible, but above the threshold, it might cause harm or adverse effects.

5. Thresholds are crucial for establishing safe limits in environmental policies, drug dosages, and occupational health standards.

6. The maximum limit beyond which harm occurs is a central concept in setting safety standards in various fields.