Final answer:
The signal word for the least hazardous pesticide is 'Caution', ranking lower in toxicity compared to 'Poison', 'Danger', and 'Warning'.
Step-by-step explanation:
The signal word that indicates the least hazardous pesticide is 'Caution'. The signal words used on pesticide labels are part of a labeling system that indicates the level of toxicity of the product. The words from highest to lowest toxicity are 'Poison', 'Danger', 'Warning', and 'Caution'. 'Poison' typically denotes a highly toxic chemical that can be lethal with a small amount, while 'Danger' may refer to products that can cause severe skin irritation or irreversible eye damage. 'Warning' signals a moderate hazard, and 'Caution' indicates a product that is less toxic or presents a relatively low hazard.
The signal word that indicates the least hazardous pesticide is Caution. Signal words are used on pesticide labels to indicate the level of hazard associated with the product. In this case, 'Caution' indicates that the pesticide has low toxicity and poses the least hazard to human health.