Equivalence is represented by

$p\Leftrightarrow q$

So,

$(a)\rightarrow(iv)$

Contrapositive of $p\Rightarrow q$ is

$\sim q\Rightarrow \sim p$

So,

$(b)\rightarrow(iii)$

Converse of $p\Rightarrow q$ is

$q\Rightarrow p$

So,

$(c)\rightarrow(ii)$

Implication is represented by

$p\Rightarrow q$

So,

$(d)\rightarrow(i)$

Therefore, correct matching is

$(a)-(iv),\ (b)-(iii),\ (c)-(ii),\ (d)-(i)$