$R1)$ Reflexive : $ a+a=2a$ always even
Symmetric: either $(a,b)$ both must be odd or both must be even to have sum as even
Therefore, if$(a,b)$ then definitely $(b,a)$
Transitive: if$(a,b)$ and $(b,c)$ , then both of them must be even pairs or odd pairs and therefore (a,c) is even
$R2)$ Reflexive : $a+a=2a$ cant be odd ever
$R3)$ Reflexive: $a.a>0$
Symmetric: if $a,b>0$ then both must be +ve or -ve, which means $b.a >0$ also exists
Transitive : if $a.b>0$ and $b.c>0$ then to have b as same number, both pairs must be +ve or -ve which implies $a.c>0$
$R4)$ Reflexive: $|a-a|\leq2$
Symmetric: if $|a-b|\leq 2$ definitely $|b-a|\leq2$ when $a,b$ are natural numbers
Transitive: $|a-b|\leq2$ and $|b-c|\leq2$, does not imply $|a-c|\leq2$
Ex: $|4-2|\leq2$ and $|2-0|\leq2$ , but $|4-0|>2$ ,
Hence, $R2$ and $R4$ are not equivalence.
Answer is $B.$