25. Both excitatory and inhibitory neurons form junctions with muscles. By what mechanism do inhibitory neurotransmitters prevent the postsynaptic cell from firing an action potential? (A) By closing Na⁺ channels (B) By preventing the secretion of excitatory neurotransmitters (C) By opening K⁺ channels (D) By opening Cl⁻ channels (E) By blocking voltage-gated Ca²⁺ channels