KVPY SA Exam 05-Nov-2017 Question Paper

Consider the following statements (X and Y stand for two different elements)
(I) ${}_{32}^{}{\mathit{X}}_{}^{65}$ and ${}_{33}^{}{\mathit{Y}}_{}^{65}$ are isotopes.
(II) ${}_{42}^{}{\mathit{X}}_{}^{86}$ and ${}_{42}^{}{\mathit{Y}}_{}^{85}$ are isotopes.
(III) ${}_{85}^{}{\mathit{X}}_{}^{174}$ and ${}_{88}^{}{\mathit{Y}}_{}^{177}$ have the same number of neutrons.
(IV) ${}_{92}^{}{\mathit{X}}_{}^{235}$ and ${}_{94}^{}{\mathit{Y}}_{}^{235}$ are isobars.
The correct statements are :