Every valid email address must contain which symbol?

The correct answer is @ (at sign). A standard email address follows the format local-part@domain. The @ symbol separates the username (local part) from the domain name.

Anatomy of an Email Address

• The @ Symbol: The at sign separates the local part from the domain. For example, in john.doe@example.com, john.doe is the local part, while example.com is the domain.

```

• Email Standard: Standard Internet email addresses use the @ symbol to separate the local part from the domain. This is a fundamental feature of the conventional email address format.
• Why the Other Options Are Incorrect:
  • # (Hash): Commonly used in URLs and other contexts, but it is not the required separator in an email address.
  • $ (Dollar sign): Not required in an email address.
  • & (Ampersand): Not required in an email address.

```

Hence, the correct answer is @ (at sign).