Explanation:

- The sentence aims to ask if both the father and elder brother are out of town.

- Option (a) features "Are not your father," which is grammatically correct. "Are not" is a proper verb construction for a question and "your father" as the subject is correct.

- Option (b) "and your elder brother" is linked properly to the subject of the sentence.

- Option (c) "out of town?" properly forms the predicate of the question.

- Option 4 (d), "No Error" is the correct choice as the sentence is grammatically correct.