Let R be the set of real numbers 
Statement-I:  $A=\{(x,y)\in R\times R/y-x\text{ is an integer}\}$ is an equivalence relation on R 
Statement-II:  $B=\{(x,y)\in R\times R/x=\alpha y\text{ for some rational number }\alpha \}$ is an equivalence relation on R.

Statement-I is true, Statement-II is true, Statement-II is the correct explanation of  Statement-I

Statement-I is false, Statement-II is true

Statement-I is true, Statement-II is false.

Statement-I is true, Statement-II is true, statement-II is not the correct explanation of Statement-I