What language does a billboard speak?

Common Wrong Answers
“English”
Billboards can be in any language, but the riddle specifically points to a form of communication that is visually conveyed, which is not limited to spoken languages.
“Spanish”
Similar to English, Spanish is a spoken language and does not capture the visual and non-verbal aspect of communication that the riddle is hinting at.
“Body language”
While body language is a form of non-verbal communication, it does not relate to the visual medium of a billboard, which uses signs and symbols, hence the answer is 'Sign language'.
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