The correct punctuation for an interrogative sentence is a question mark (?). The question mark is a punctuation mark that is used at the end of a sentence to indicate that it is a question. It is important to use the question mark correctly in order to convey the intended meaning of the sentence.

Here is an explanation of why the question mark is the correct punctuation for an interrogative sentence:

1. Purpose of interrogative sentences:
Interrogative sentences are used to ask questions and seek information. They are usually formed by inverting the subject and the auxiliary verb, or by using a question word (such as who, what, where, when, why, or how) at the beginning of the sentence. The purpose of an interrogative sentence is to prompt a response.

2. Differentiating interrogative sentences:
Using the correct punctuation is essential for differentiating between different types of sentences. When we use a question mark at the end of a sentence, it signals that the sentence is an interrogative sentence and requires an answer or a response. This helps the reader or listener understand that the sentence is not a statement or a command, but a question.

3. Importance of clarity and understanding:
Using the correct punctuation, such as the question mark, is crucial for clarity and understanding in written communication. Without the question mark, it may be difficult for the reader to discern whether a sentence is a question or a statement. By using the question mark, we ensure that the intended meaning of the sentence is conveyed accurately.

In conclusion, the correct punctuation for an interrogative sentence is a question mark (?). This punctuation mark is used to indicate that a sentence is a question and prompts a response. Using the question mark correctly helps ensure clarity and understanding in written communication.