Basic General Knowledge
The official languages of the United Nations are

Arabic, Japanese, Chinese, English, French and German
Chinese, English, French, Hindi, Japanese and Spanish
African, Chinese, English, French, German and Spanish
Arabic, Chinese, English, French, Russian and Spanish

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Basic General Knowledge
To produce sound it is necessary that

the vibrations of source are not necessary
the source should execute longitudinal vibrations
the source may execute any type of vibrations
the source should execute transverse vibrations

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