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Two main types of GABA receptors mediate inhibition in the brain, and they work through different mechanisms. GABA-A receptors are ionotropic, forming a ligand-gated chloride channel. When GABA binds, chloride ions flow into the neuron, hyperpolarizing it and producing fast, brief inhibitory postsynaptic potentials. GABA-B receptors are metabotropic, meaning they are G-protein-coupled receptors that influence ion channels and intracellular signaling through second messengers, typically opening potassium channels or reducing calcium influx, which leads to slower, longer-lasting inhibition. Therefore, the statement that GABA-A is ionotropic and GABA-B is metabotropic is the correct description. The other pairings would imply opposite or double-mechanism roles that aren’t accurate.