An undersupply of the major inhibitory neurotransmitter known as is linked to seizures.

Gamma-aminobutyric acid (GABA)

Explanation:

Epileptic seizures are induced by a preponderance of electrical activity within the network of neurons in the brain. Synapsis is the meeting point between the axon of one neuron and the dendrite of another neuron. Electrical signals don't cross through the synapsis, instead, they are conveyed in a chemical form by neurotransmitters.

The neurotransmitters convey messages across the synapsis in a chemical form until they find to the receptor of the dendrite of the receiving neuron. Neurotransmitters can either be excitatory or inhibitory in function i.e. the receiving neuron can either be stimulated to action or inhibited from action. The main excitatory and inhibitory neurotransmitters in the brain are Glutamate and Gamma-aminobutyric acid (GABA) respectively.

There must be a balance between excitation and inhibition of neurons, in order to ascertain the optimal functioning of the brain. Too much Glutamate or too little of GABA can make neurons hyperexcitable and hyperexcitability of neurons makes the brain susceptible to seizures.

"d.) carbon dioxide and hydrogen sulfide"

stimulus is a change in the environment that causes an organism to react. the response is the reaction to the stimulus. some examples of stimuli for zebras are drought, to many predators, and bad feeding grounds such as dead grass or plants. zebras respond to stimuli just like all other living organisms