与公式(“x)(P(x)∧Q(x, y))Þ($x)R(x, y)等值的是()
A. (“x)(P(x)∧Q(x, z))Þ($x)R(x, y)
B. (“y)(P(y)∧Q(y, y))Þ($x)R(x, y)
C. (“z)(P(z)∧Q(x, y))Þ($x)R(x, y)
D. (“u)(P(u)∧Q(u, z))Þ($x)R(x, z)
谓词公式(“x)F(x) Þ (“x)G(x)的前束范式是()
A. (“x)(“y) (F(x) Þ G(y))
B. ($x)(“y)(F(x) Þ G(y))
C. (“x)($y) (F(x) Þ G(y))
D. ($x)($y)(F(x) Þ G(y))