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