Which of the following is considered a highly toxic pesticide?

Chlorpyrifos is recognized as a highly toxic pesticide primarily due to its classification as an organophosphate. This group of chemicals works by inhibiting the enzyme acetylcholinesterase, leading to an accumulation of acetylcholine in the nervous system, which can result in severe neurological effects in both insects and non-target organisms, including humans. Due to its high toxicity profile and potential for harmful effects on human health, particularly in children, the use of chlorpyrifos has become heavily restricted in many regions, and it is often regulated strictly due to environmental concerns as well.

In contrast, the other options present alternative profiles. Imidacloprid, an insecticide that belongs to the neonicotinoid class, has lower acute toxicity relative to chlorpyrifos but still poses risks to pollinators and certain non-target species. Diatomaceous earth, a natural pest control agent, is generally considered safe for use around humans and pets, primarily affecting insects by damaging their exoskeletons rather than through toxicological pathways. Bacillus thuringiensis is a bacterium used as a biological control agent against certain pests; it is considered safe because it specifically targets insect larvae without posing toxicity to humans and other