Which scan type updates tracking information every 2 (2 lobes) to 4 (4 lobes) pulses?

The choice indicating "Sequential Lobing" is correct because this scan type is designed to update tracking information by using a series of lobes that are sequentially illuminated. Each lobe is associated with a separate measurement, and the system can use the data collected from 2 to 4 lobes per pulse to refine its targeting information.

Sequential Lobing operates by directing the radar beam through a series of predefined angles, allowing for quick updates on the target's position. This method is efficient as it allows the radar to gather important data without having to continuously sweep the entire area, providing updates every 2 to 4 pulses as needed. This characteristic makes Sequential Lobing effective for tracking moving targets while still maintaining situational awareness.

In contrast, the other options refer to different scanning and tracking methods that do not specifically update tracking information in the same way or at the same frequency. For example, Monopulse tracks targets more precisely in a single pulse rather than in a series of lobes, and Track While Scan operates by maintaining track on a target while sweeping the search area, often not tied to the pulsing method described in the question.