Select the correct statement.

• A
  In an Ellingham diagram,if a metal $M$ is present below the line of another metal oxide $M'O$,then metal $M$ is a good reducing agent for $M'O$.
• B
  Due to the basic nature of the oxides of alkaline earth elements,they combine with atmospheric acidic oxides to form salts.
• C
  Both are correct.
• D
  None is correct.