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

• A

  $a{R}_{1}b\iff \left|a\right|=\left|b\right|$

• B

  $a{R}_{2}b\iff a\ge b$

• C

  $a{R}_{3}b\iff a\text{ divides }b$

• D

  $a{R}_{4}b\iff a<b$