The correct answer is (D) Specialized language; the vocabulary of a specialized trade, profession, or field. Also, unintelligible words, conversation, or writing. Also, meaningless talk, gibberish, or debased language.

Jargon comes from Middle English jargoun, from Old French.

Examples of use:

• At times, it seem that they are unable to converse in anything but jargon.
• I believe that the excessive use of jargon is a symptom of mental laziness.