Regional variations of a language are called the of that language. slang jargon dialects idioms

Dialects are the regional variations of a language.

Explanation:

Variety of language that has different vocabulary, grammar or pronunciation is dialect. It differs from one region to the other (of the persons speaking same language but has different dialect). For example, Cantonese in Guangzhou, a city of China to the Mandarin (Standard language of China) is a dialect.

Whereas, slang is an informal form of a language; jargon is the specialized language that is only used and understood by persons in the same profession or group. Idioms are the group of words that delivers meaning that is non-deducible from the individual words. So, Dialects is the right answer.

explanation:

the silver bells of the sleds are merry and keep time in the winter nights while the sky twinkles happily. the golden bells of weddings are delightful in their peaceful happiness, foretelling a rapturous future. meanwhile, the brazen alarm bells scream frightfully in the night, with a discordant and desperate sound. in their clamor, these bells convey terror, horror, and anger. finally, the iron bells are solemn and melancholy, while those in the church steeple are like ghouls who feel happiness. the king of the ghouls, who rings the bells, cheerfully keeps time with the moaning and groaning bells.