The fusion of chromite ore $(FeCr_{2}O_{4})$ with $Na_{2}CO_{3}$ in air gives a yellow solution upon addition of water. Subsequent treatment with $H_{2}SO_{4}$ produces an orange solution. The yellow and orange colours,respectively,are due to the formation of

• A
  $Na_{2}CrO_{4}$ and $Na_{2}Cr_{2}O_{7}$
• B
  $Cr(OH)_{3}$ and $Na_{2}Cr_{2}O_{7}$
• C
  $Cr_{2}(CO_{3})_{3}$ and $Fe_{2}(SO_{4})_{3}$
• D
  $Cr(OH)_{3}$ and $Na_{2}CrO_{4}$