In which of the following cases will the acidic character of a carboxylic acid be the highest?

• A
  Lower $K_a$ and $pK_a$ values
• B
  Lower $K_a$ value and higher $pK_a$ value
• C
  Higher $K_a$ value and lower $pK_a$ value
• D
  Higher $K_a$ and $pK_a$ values