Which of the following is not detected by the CMWS with HFI-enabled ECU?

The correct choice is that grenades are not detected by the CMWS (Countermeasure Warning System) with HFI (High Frequency Interface) enabled Electronic Control Unit (ECU). The CMWS is primarily designed to detect incoming threats such as missiles, rockets, and shells using advanced sensors. These systems utilize infrared technology to identify the heat signatures associated with the specific threats, allowing them to respond effectively to incoming projectiles.

Grenades, in contrast, are typically considered short-range threats that may not produce the same detectable signatures that CMWS is calibrated to recognize, especially given their smaller size and the nature of their launch mechanisms. Consequently, while the CMWS can effectively detect missiles, rockets, and artillery shells that follow predictable trajectories and exhibit distinctive heat signatures, grenades fall outside the typical operational range of this system. This distinction highlights the CMWS's limitations regarding the types of threats it can reliably identify in the battlefield environment.