题目

 ---Does China have cultural relics? --- Yes, it is admitted that many cultural relics in the world, such as the Great Wall, the Potala Palace, the Magao Caves and so on, ______ China. A. belongs to   B. are belonging to  C. belonged to   D. belong to 答案：D甘氨酸是脊髓中主要的抑制性神经递质，能使突触后膜Cl－通道开放，使Cl－内流。下列叙述正确的是A．脊髓神经元细胞静息状态时膜内外没有离子进出B．甘氨酸以自由扩散的方式经突触前膜释放到突触间隙C．甘氨酸与突触后膜上受体结合后引起膜外电位由正变负D．某种毒素可阻止神经末梢释放甘氨酸，从而引起肌肉痉挛