Let \( R \) be a relation on \( \mathbb{Z} \times \mathbb{Z} \) defined by \( (a,b)\,R\,(c,d) \) if and only if \( ad-bc \) is divisible by \( 5 \). Then \( R \) is:
Reflexive and symmetric but not transitive
Reflexive but neither symmetric nor transitive
Reflexive and transitive but not symmetric
Reflexive, symmetric and transitive