According to the representation of global biodiversity proportions for the number of species of major taxa of vertebrates,select the appropriate option for the labels $X$,$Y$,and $Z$ in the given figure.

• A
  $X$ - Mammals,$Y$ - Birds,$Z$ - Amphibians
• B
  $X$ - Birds,$Y$ - Amphibians,$Z$ - Reptiles
• C
  $X$ - Reptiles,$Y$ - Amphibians,$Z$ - Birds
• D
  $X$ - Amphibians,$Y$ - Birds,$Z$ - Mammals