Statement $(A)$: The pyramid of energy is always upright.
Reason $(R)$: Some energy is always lost as heat at each step.

• A
  $A$ is wrong and $R$ is right.
• B
  $A$ and $R$ both are true but $R$ is not the correct explanation of $A$.
• C
  $A$ is right and $R$ is wrong.
• D
  $A$ and $R$ both are true, $R$ is the correct explanation of statement-$A$.