Which components together identify an email address in the format [billybob] [@] [mailbox.com]?

An email address is structured in a specific format that consists of three essential components: the local part, the "@" symbol, and the domain part. In the given example, "[billybob]" represents the local part, "[@]" is the separator, and "[mailbox.com]" indicates the domain part.

For an email address to be valid and functional, all three components must be combined. The local part provides the name of the user or account within a given domain, while the "@" symbol indicates the separation between the user's name and the domain. The domain part specifies the mail server that will handle the email.

Individually speaking, each component is important but does not represent a complete email address on its own. The local part without the domain would not lead to a valid email address, and similarly, having just the domain, or just the "@" symbol would also lack the necessary information to identify a complete address. Therefore, the correct understanding is that all three components together are required to identify an email address accurately.