A. Ulta Narrow Band (UNB)
B. Universal Narrow Band (UNB)
C. Global Narrow Band (GNB)
D. Local Narrow Band (LNB)

Solution

A. Ulta Narrow Band (UNB)

Explanation

Sigfox uses an ultra-narrow band modulation technique, which allows for long-range communication with minimal power consumption. The narrow band is a key feature that contributes to the network's efficiency and ability to penetrate obstacles.