Step-by-step Solution:

The word swanky means stylish, luxurious, or fashionable. Among the given options, the most suitable synonym is:\[\](a) posh - This means elegant or luxurious, which aligns with the meaning of swanky.\[\] (b) poor - This indicates a lack of resources or quality, which is the opposite of swanky.\[\] (c) plain - This means simple or unadorned, which does not match the luxurious connotation of swanky.\[\] (d) modest - This \(\implies\) humility or simplicity, which is contrary to the flamboyant nature of swanky.\[\] \[\] Correct Answer: (a)