The answer is: C
Explanation
The correct option is C: A, B and C.
This is because according to Order 9 Rule 13 of the Code of Civil Procedure, 1908, an ex parte decree can be set aside if the summons was not duly served or the defendant was prevented by sufficient cause from appearing in the court. In this case, A and B did not receive the summons, so they have a valid ground to set aside the ex parte decree. However, C also received the summons, but did not appear in the court. Therefore, C cannot apply to set aside the ex parte decree on his own. However, if A and B apply to set aside the ex parte decree, it will also benefit C, as the decree was passed jointly against all the coparceners. This is based on the principle of joint liability and benefit of the coparceners in a Hindu joint family. Therefore, the decree will be set aside against A, B and C. This is supported by the case of Nanda Dulal Pradhan & Anr. v. Dibakar Pradhan & Anr., 2022, where the Supreme Court held that an ex parte decree passed against a joint Hindu family can be set aside if any of the coparceners did not receive the summons.