$A$ hydrated solid $X$ on heating initially gives a monohydrated compound $Y$. $Y$ upon heating above $373 \ K$ leads to an anhydrous white powder $Z$. $X$ and $Z$,respectively,are

• A
  Washing soda and soda ash.
• B
  Washing soda and dead burnt plaster.
• C
  Baking soda and dead burnt plaster.
• D
  Baking soda and soda ash.