Explanation

• Structure of DNA was discovered by James Watson and Francis Crick in 1953.
• They discovered the double-helix structure of DNA using X-ray crystallography data.
• Their discovery revealed the double-helix structure of DNA, where two complementary strands are twisted together with sugar and phosphate molecules, and the nitrogenous bases (adenine, thymine, cytosine, and guanine) pair in a specific manner.

Explanation

• Sunspots were first observed telescopically in late 1610 by Thomas Harriot and Italian polymath Galileo Galilei
• Sunspots are dark areas on the Sun’s surface caused by lower temperatures and strong magnetic activity.

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Explanation

Braun was a German-born American aerospace engineer and space architect. 

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 Allen Shepherd became the first American to travel into space in 1961, and in 1971, he walked on the Moon.

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Galileo Galilei was an Italian astronomer, physicist and engineer.

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Videotape is magnetic tape used for storing video and usually sound in addition. Information stored can be in the form of either an analog signal or digital signal.

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The noun discovery means the finding or uncovering of something.

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Karl  Benz was a German engine designer and automobile engineer.

His Benz Patent Motorcar from 1885 is considered the first practical automobile.

Explanation

Radium is a chemical element with the symbol Ra and atomic number 88.