How to check boolean in table with a corresponding name?

Hi. I'm making a keycard system and I need to know how to read a table that works something like this

local cards = {
    ["a"] = true,
    ["b"] = true,
    ["c"] = true,
    ["d"] = false,
    ["e"] = true,
    ["f"] = false
}

and return if it's true or false, and call it for any of the keycards. I really can't get my finger on how to do this, and any help would be appreciated! Thanks!