()(R(x)→(y)Q(x,y))的前束范式是
A (y) () (┐R(x)∧Q(x,y))
B ()(y) (┐R(x)∧Q(x,y))
C (y) ()(┐R(x)∨Q(x,y))
D ()(y) (┐R(x)∨Q(x,y))