To answer this question, you need to understand computer abbreviations.

Option A) Order of Significance - This option is incorrect because in the context of computers, the abbreviation 'OS' does not refer to the order of significance.

Option B) Open Software - This option is incorrect because although 'OS' can be associated with open-source software, it is not the most common or widely known abbreviation for open software.

Option C) Operating System - This option is correct. In the context of computers, 'OS' typically refers to the abbreviation for "Operating System." An operating system is a software that manages computer hardware and software resources and provides common services for computer programs.

Option D) Optical Sensor - This option is incorrect because 'OS' is not a commonly used abbreviation for optical sensor.

The correct answer is C) Operating System. This option is correct because 'OS' typically stands for Operating System in the context of computers.

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To answer this question, we need to understand when the first transatlantic radio broadcast occurred.

Option A) 1850s - This option is incorrect because the first transatlantic radio broadcast did not occur in the 1850s. During this time, radio technology was not yet developed enough for transatlantic communication.

Option B) 1860s - This option is incorrect because the first transatlantic radio broadcast did not occur in the 1860s. Radio technology was still in its early stages of development during this decade.

Option C) 1870s - This option is incorrect because the first transatlantic radio broadcast did not occur in the 1870s. While there were advancements in telegraphy during this time, transatlantic radio communication was not yet achieved.

Option D) 1900s - This option is correct because the first transatlantic radio broadcast occurred in the 1900s. Specifically, the first transatlantic radio transmission took place on December 12, 1901, when Guglielmo Marconi successfully transmitted a radio signal across the Atlantic Ocean from Poldhu, Cornwall, in England to St. John's, Newfoundland, in Canada.

The correct answer is D. The first transatlantic radio broadcast occurred in the 1900s.

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