Which of the following is a sign of overexcitement of nerves and muscles due to pesticide exposure?

Muscle twitching is a sign of overexcitement of nerves and muscles due to pesticide exposure because it reflects the overstimulation of the nervous system. Pesticides, particularly those classified as organophosphates and carbamates, inhibit enzymes responsible for breaking down neurotransmitters, leading to an accumulation of these chemicals in the synapses. As a result, the muscles may receive continuous signals to contract, which manifests as twitching or spasms.

While dry mouth, excessive sweating, and nausea can also occur with pesticide exposure, they are not as directly indicative of nerve and muscle overstimulation. Dry mouth may result from various factors, including dehydration or other systemic responses but doesn't specifically indicate nerve activity. Excessive sweating can be a response to a variety of conditions, including stress or heat, and may not solely point toward nerve overstimulation. Nausea is a general symptom that can arise from many forms of chemical exposure or irritation of the gastrointestinal tract rather than being a direct sign of nervous system distress. Thus, muscle twitching specifically highlights the underlying problem of nerve and muscle overexcitement related to pesticide contact.