The correct answer is the 'DDR3 1600MHz' module, as it matches the maximum supported frequency by the older workstation's motherboard. Installing a module with a higher frequency like 'DDR3 1866MHz' or a lower frequency like 'DDR3 1333MHz' would either potentially create incompatibility issues or degrade performance. Using a different RAM type, such as 'DDR2', would physically not fit in the DDR3 slot due to different notches and key placements on the DIMM compared to DDR3, preventing proper installation.