Final answer:
Wall and floor mounts are acceptable for a modem, but ceiling and inverted mounts are not, due to potential issues with signal transmission, access, and device maintenance.
Step-by-step explanation:
The acceptable mounting systems for a modem typically include a wall mount, floor mount, or even placement on a shelf or desk. Ceiling mounts are generally not preferred or recommended for modems, as this could lead to difficulty with cable management, interference with signal transmission, and challenges in accessing the device for troubleshooting or maintenance. An inverted mount, where the modem is mounted with its ports facing downwards, is also not an acceptable mounting system, as it could lead to accumulation of dust in the ports and potential overheating due to poor ventilation.