The number of electrons, protons and neutrons in a species are equal to 38,38 and 50 respectively.  The proper symbol to the species is

• A

  ${\mathrm{Sr}}_{38}^{88}$

• B

  ${}_{38}{}^{50}\mathrm{Sr}$

• C

  ${\mathrm{Sr}}_{50}^{88}$

• D

  ${\mathrm{Sr}}_{88}^{50}$