Given below are two statements:
Statement $I$: $A$ buffer solution is the mixture of a salt and an acid or a base mixed in any particular quantities.
Statement $II$: Blood is a naturally occurring buffer solution whose $pH$ is maintained by $H_2CO_3 / HCO_3^{-}$ concentrations.
In the light of the above statements,choose the correct answer from the options given below.

• A
  Statement $I$ is false but Statement $II$ is true
• B
  Both Statement $I$ and Statement $II$ are true
• C
  Both Statement $I$ and Statement $II$ are false
• D
  Statement $I$ is true but Statement $II$ is false