Which one of the following Boolean expressions is NOT a tautology?

A

$$((a \rightarrow b) \wedge (b \rightarrow c)) \rightarrow (a \rightarrow c)$$

B

$$(a \leftrightarrow c) \rightarrow (\sim b \rightarrow (a \wedge c))$$

C

$$(a \wedge b \wedge c) \rightarrow (c \vee a)$$

D

$$a \rightarrow (b \rightarrow a)$$