Comprehensive Detailed Explanation:

Microwave sensors, which work by emitting electromagnetic waves and detecting changes in the reflected signal, are most effective when a target moves laterally (side-to-side) across the detection zone. This movement creates the greatest frequency shift (Doppler effect), making it easier for the sensor to detect motion.

Movement directly toward or away (C) causes minimal frequency change and can go undetected.

Speed (B or D) matters, but direction relative to the sensor is the key factor for detection efficiency.