Identify the pairs which are not of isotopes

Options

A. `._(6)^(12)X ,._(6)^(13)X`
B. `._(17)^(35)X ,._(17)^(37)X`
C. `._(6)^(14)X ,._(7)^(14)X`
D. `._(4)^(8)X ,._(5)^(8)X`

Explanation

(A) `._(6)^(12)X` and `._(6)^(13)Y` have same atomic number but different mass number. (B) `._(17)^(35)X` and `._(17)^(37)Y` have same atomic number but different mass number. So, these both pairs are isotopes to each other.(C) `._(6)^(14)X` and `._(7)^(14)Y` have different atomic number but same mass number. (D) `._(4)^(8)X` and `._(5)^(8)Y` have different atomic number but same mass number. So, these both pairs are isobars to each other.