Yuri Gagarin made a successful space flight in 1961. Humans uncertainties about universe were enlightened only then.

Explain:

Yuri Gagarin successfully made a space flight in 1961. Human uncertainties about the universe were only enlightened then.

A. Wrong grammar

B. Without human uncertainties about the universe, Yuri Gagarin would have failed to make a space flight in 1961.

C. It was not until human uncertainties about the universe were cleared up that Yuri Gagarin successfully made a space flight in 1961.

D. It was only after Yuri Gagarin successfully made a space flight in 1961 that human uncertainties about the universe were enlightened.

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