Final answer:
A remote pilot should use visual scanning to monitor for traffic, since other methods like radar scanning are often not available on small unmanned aerial systems.
Step-by-step explanation:
The technique that a remote pilot should use to scan for traffic is visual scanning. This involves continuously observing the airspace for other aircraft as part of the pilot's responsibility to see and avoid other aircraft. While radar scanning is useful in certain contexts for determining the distance to objects, like aircraft or weather formations, and is a common application of microwaves, it is typically used by ground-based operators or on larger aircraft with equipped radar systems. Remote pilots, especially those operating small unmanned aerial systems (drones), usually rely on visual scanning, as these drones do not have radar capabilities and the pilot is not in the aircraft to use onboard radar. Remote pilots can also use radio scanning to some extent, which involves listening to relevant communication frequencies for traffic advisories but is secondary to visual scanning when it comes to collision avoidance.