Which one of the following relations on R is an equivalence relation

• A

  ${\mathrm{aR}}_1\mathrm{b}\iff \left|\mathrm{a}\right|=\left|\mathrm{b}\right|$

• B

  ${\mathrm{aR}}_2\mathrm{b}\iff \mathrm{a}\ge \mathrm{b}$

• C

  ${\mathrm{aR}}_3\mathrm{b}\iff \mathrm{a} \mathrm{divides} \mathrm{b}$

• D

  ${\mathrm{aR}}_4\mathrm{b}\iff \mathrm{a}<\mathrm{b}$