@owashii@plush.city actually, legitimately, the answer is e
the letter g was a late addition to the roman alphabet. for a very long time the letter C was used for both /k/ and /g/, and then later this one emperor just said "no you're going to use this modified C now when it means /g/" which is why you get ancient Roman names in pairs like Caius/Gaius and Cnaeus/Gnaeus
that same guy also invented like two or three other new letters but they didn't stick around
-F