Which of the following is a warning used on labels of slightly toxic pesticides?

In the context of pesticide labeling, the term "Caution" is specifically used to indicate the level of toxicity associated with slightly toxic pesticides. Pesticides are classified according to their toxicity levels, which helps guide handlers and users on the safety measures they should implement when using these products.

The label categories represent a hierarchy of toxicity, with "Caution" being the lowest level of concern. Slightly toxic pesticides fall into this category, meaning they are less hazardous than those that would require a more severe label warning, such as "Warning" or "Danger." These latter labels are associated with more severe toxicity levels and imply a greater risk to humans and the environment.

The option "Notice" is not a standardized warning term used on pesticide labels and does not convey a specific level of toxicity. Therefore, "Caution" is the correct choice, as it accurately corresponds to the label designation for slightly toxic pesticides, signifying that while some precautions are necessary, the risks are not as pronounced as they would be for more toxic substances.