C. 500W redundant power supply
A redundant power supply is designed to provide backup power in case one power supply unit fails. In a scenario where the management team has not decided on installing dual graphics cards, a 500W redundant power supply would be a good solution. It provides redundancy to ensure continuous power supply in case one unit fails, and it has sufficient wattage (500W) to handle the power requirements of workstations, including the possibility of dual graphics cards in the future.
Options A and B are not specifically redundant power supplies. Option D, the 2000VA uninterruptible power supply (UPS), is designed to provide backup power in case of outages but doesn't inherently provide redundancy like a redundant power supply would.