This might seem to be about as pedantic as it's possible to get, but the symbol commonly used to refer to the speed of light is a lower case 'c'. The answer gives it in upper case; I wouldn't be surprised if some over-zealous question asker wanted to know if it was upper or lower case.
And while we're on the subject of pedantry: is it actually a mathematical symbol? Granted, it's the symbol used in equations; but you could argue that it's more than that. Wikipedia simply states that the speed of light is "commonly denoted c".
The question could have asked "What symbol is commonly used to denote the speed of light?" The most correct answer would be "A lower case c", but it would be very harsh not to accept just "c".
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