Final answer:
A parabolic antenna is the best choice for a network technician looking to link two buildings with a wireless connection utilizing 802.11ac, due to its small footprint, minimal weight, and directional focus.
Step-by-step explanation:
A network technician looking to create a wireless link between two office buildings utilizing the 802.11ac standard should opt for an antenna that has a small physical footprint and minimal weight. Given these requirements, the best choice would be a parabolic antenna. Parabolic antennas are highly directional, meaning they can focus a signal tightly between two points, which is ideal for linking two distinct locations. Additionally, they can be designed to be relatively lightweight and compact, especially when compared to other highly directional antennas such as the Yagi. While Yagi antennas are also directional, they tend to have a larger physical size because of their multiple elements. Omni-directional antennas would not be suitable as they disperse the signal in all directions, reducing the strength of the link between specific points. Lastly, patch antennas could be considered, but they may not provide the requisite range and directivity needed for the inter-building link. Therefore, the parabolic antenna is the most suitable option for this scenario.