数控编程指令G02X---Y---R不能用于（）加工。
A.1/4圆
B.1/2圆
C.3/4圆
D.整圆
参考答案：D
Explain and distinguish between the following terms in relation to the doctrine of precedent in the Scottish legal system:
(a) ratio decidendi and obiter dictum; (4 marks)
人参具有中枢兴奋作用的化学成分是（）.
A．人参皂苷Ra类
B．人参皂苷Rb类
C．人参皂苷Re类
D．人参皂苷Rf类
E．人参皂苷Rg类
