The nuclei of which one of the following pairs of nuclei are isotones

${ }_{34} \mathrm{Se}^{74},{ }_{31} \mathrm{Ca}^{71}$

${ }_{42} M o^{92},{ }_{40} Z r^{92}$

${ }_{38} S r^{81},{ }_{38} S r^{86}$

${ }_{20} \mathrm{Ca}^{40},{ }_{16} \mathrm{~S}^{32}$