Let R be the real line. Consider the following subsets of the plane `RxxR` . `S""=""{(x ,""y)"":""y""=""x""+""1""a n d""0""<""x""<""2},""T""=""{(x ,""y)"":""x-y""` is an integer }. Which one of the following is true? (1) neither S nor T is an equivalence relation on R (2) both S and T are equivalence relations on R (3) S is an equivalence relation on R but T is not (4) T is an equivalence relation on R but S is not

Options

A. Both S and T are equivalence relations on R
B. S is an equivalence relation on R but T is not
C. T is an equivalence relation on R but S is not
D. Neither S nor T is an equivalence relations on R

Answer

C

Explanation

`T={(x,y):x-yinI}`
As `0 in I`, so T is a reflexive relation
If `x-yinIimpliesy-x inI`
`therefore` T is symmetric also.
If x - y = I and y - z = 12
Then, `x-z=(x-y)+(y-z)=I_(1)+I_(2)inI`
`therefore` T is also transitive.
Hence, T is an equivalence relation. Clearly, `xnex+1implies(x,x)cancelinS`
`thereforeS` is not reflexive.