Why is the engineer unable to locate the offending device or devices?

While performing a Layer 1 passive wireless site survey of a location an engineer detects several instances of low power frequency hopping interference, but cannot physically locate the interfering device or devices.

Why is the engineer unable to locate the offending device or devices?
A . The sources are nearby narrow-beam radar and are sweeping through the facility.
B . The sources are PAN and are mobile.
C . The sources are above the ceiling file and transmit intermittently.
D . The sources are actually high-powered devices and transmit from off the site.

Answer: B