使用下述谓词:P(x): x是熊猫、Q(x): x是飞鸟、R(x): x是绿色的,及量词表示自然语句“没有熊猫是绿色的话,就至少有一只飞鸟存在”为()
A. ~($x)(P(x)∧R(x)) Þ ($x) Q(x)
B. ~($x)(P(x) Þ R(x)) Þ ($x) Q(x)
C. ~($x)(P(x)∧R(x)) ∧ ($x) Q(x)
D. ~($x)(P(x) Þ R(x)) ∧ ($x) Q(x)
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)