What is the primary purpose of an antenna in communication systems?

The primary purpose of an antenna in communication systems is to transmit data via electromagnetic waves. Antennas are designed to convert electrical energy into electromagnetic waves for transmission, and conversely, they can also receive electromagnetic waves and convert them back into electrical signals. This functionality is crucial for enabling wireless communication, as antennas facilitate the transfer of data over various distances without the need for physical connections.

When discussing other options, converting sound to electrical signals is typically the role of a microphone rather than an antenna. Filtering signals is a function usually associated with radio receivers and electronic circuits that separate desired signals from unwanted noise but does not define the antenna's primary function. Storing electrical energy is generally related to capacitors or batteries, not antennas, which are more focused on the transmission and reception of signals rather than energy storage.

Thus, the correct choice underscores the fundamental role of antennas in communication systems as vital components in the transmission of information through electromagnetic waves.