—My cousin bought me aft English learnin
题型：选择题
问题：
—My cousin bought me aft English learning machine, but I don't know ________.
—Don't worry. Just follow the instruction. [ ]
A. how to use it
B. which one to choose
C. when to use it
题型：选择题
下图是反射弧模式图，X、Y为神经纤维上的实验位点，Z为突触间隙。回答下列问题：
某种药物可以阻断青蛙屈肌反射活动。将药物放在X处，刺激Y，肌肉收缩；将药物放在Z，刺激Y，肌肉不收缩。该实验结果证明这种药物在神经系统中仅对兴奋在（）的传导有阻断作用。