A-3. If horses whinny, cows moo. So if cows don't moo, horse don't whinny.

Writing "H" for "Horses whinny", "C" for "Cows moo"

If horses whinny, cows moo. 符號化後：H⊃C

if cows don't moo, horse don't whinny.符號化後：–C⊃–H

每種前提為真的情況下，結論皆為真。因此論證有效。

B-1

p&q; q

由上述真值表可知：p&q蘊含了q