Which of the following is not a data transmission method?

The correct choice identifies "Linkcast" as not being a recognized data transmission method. In networking, the commonly used data transmission methods include broadcast, unicast, and multicast.

Broadcasting allows data to be sent from one source to all devices on a network segment. This method is useful for scenarios where information needs to be distributed to every device without requiring individual transmission paths.

Unicast refers to a one-to-one communication method where data is transmitted from a single source to a single destination. It's the most common form of communication, particularly in situations like point-to-point video calls or direct file transfers.

Multicast is used for one-to-many or many-to-many transmission, where data is sent from one source to multiple specified destinations simultaneously, which optimizes bandwidth usage for applications such as streaming video to multiple viewers.

In contrast, "Linkcast" does not exist as a standard term or method within networking literature. Therefore, it can be concluded that it doesn't fit within the recognized categories of data transmission, making it the correct answer in this question.