5. 突觸前抑制(presynaptic inhibition)發生於何處? (A)軸突-軸突性(axo-axonic)突觸 (B)軸突-樹突性(axo-dendritic)突觸 (C)軸突-本體性(axo-somatic)突觸 (D)樹突-樹突性(dendro-dendritic)突觸