The following figure shows the stomatal apparatus. Identify the parts labelled as $A, B, C$ and $D$. Choose the correct answer from the following.

• A
  $A = \text{Subsidiary cells}, B = \text{Chloroplasts}, C = \text{Stoma}, D = \text{Guard cells}$
• B
  $A = \text{Guard cells}, B = \text{Stoma}, C = \text{Chloroplasts}, D = \text{Subsidiary cells}$
• C
  $A = \text{Subsidiary cells}, B = \text{Stoma}, C = \text{Chloroplasts}, D = \text{Guard cells}$
• D
  $A = \text{Guard cells}, B = \text{Chloroplasts}, C = \text{Stoma}, D = \text{Subsidiary cells}$