Which of the following pairs of molecules have practically the same mass ?

• A

  ${\mathrm{D}}_2\mathrm{O} \mathrm{and} {\mathrm{H}}_2\mathrm{O}$

• B

  ${\mathrm{H}}_2\mathrm{O} \mathrm{and} \mathrm{HTO}$

• C

  ${\mathrm{D}}_2\mathrm{O} \mathrm{and} \mathrm{HTO}$

• D

  DTO and HDO