Let $a,b$ be logic propositions. In the truth table for $a,b$ whenever $a=T$ then $b=F$ and when $b=F$ then $a=T$. Which of the below statements is true:
$a\to b$ is a tautology
$a\to b$ is a contradiction
$a \lor b$ is a contradiction
$a \iff b$ is a contradiction
none of the statements are correct
I think that 4) is correct that is $a \iff b$ is a contradiction because of the given that $a$ and $b$ are always the opposite of each other and $\iff$ requires both sides to be true.
But I'm not sure.