Solution

An email address is formatted as username@domain.extension. In the example:

• sample: The username.
• gmail: The domain name.
• .com: The extension (Top-Level Domain, or TLD).

The other options are incorrect:

• sample@gmail@com: Contains two @ symbols, which is not allowed in email addresses.
• www.sample.com: This is a web address (URL), not an email address.
• http.sample.com: Also resembles a web address or link, not an email address.

Therefore, the correct format for an email address is sample@gmail.com.