Which of the following is a valid long-distance dialing format?

The choice indicating that the valid long-distance dialing format is "1 + area code + seven-digit number" is correct because this is the standard format used in North America for placing a long-distance call. In this format, the "1" is the long-distance prefix that indicates you are making a long-distance call, followed by the three-digit area code for the destination, and then the seven-digit local phone number.

The significance of this format lies in its consistency and recognition, making it straightforward for both callers and telecommunication providers to process long-distance calls effectively. This system ensures that calls are routed correctly across the telephone network.

In contrast, the other options involve either using the wrong dialing prefix for standard long-distance calls or incorrect configurations that do not correspond to valid dialing practices. For example, using '0' generally indicates operator-assisted dialing rather than direct long-distance calling, and using '411' is designated for directory assistance rather than dialing a specific local number. Thus, understanding the structure of long-distance calling is essential for effective communication.