Most of the classmates couldn’t come. He invited them to the birthday party.

• A. 
  Most of the classmates he invited to the birthday party couldn’t come.
• B. 
  Most of the classmates he was invited to the birthday party couldn’t come.
• C. 
  Most of the classmates that he invited them to the birthday party couldn’t come.
• D. 
  Most of the classmates which he invited to the birthday party couldn’t come.