The statements that are $TRUE$:
$A$. Methane leads to both global warming and photochemical smog.
$B$. Methane is generated from paddy fields.
$C$. Methane is a stronger global warming gas than $CO_2$.
$D$. Methane is a part of reducing smog.
Choose the most appropriate answer from the options given below:

• A
  $A, B, C$ only
• B
  $A$ and $B$ only
• C
  $B, C, D$ only
• D
  $A, B, D$ only