Final answer:
The best way to rewrite Sentence 3 is: 'At that time, in the 1950s and 1960s, the first requirement to being a military test pilot was being male.' This option effectively structures the sentence to provide immediate clarity on the time period and the requirement.
Step-by-step explanation:
In order to create a clear and properly structured sentence, the best way to rewrite Sentence 3 would be: Option 4) At that time, in the 1950s and 1960s, the first requirement to being a military test pilot was being male. This sentence places the time context, 'the 1950s and 1960s' immediately after 'at that time', providing immediate clarity about the period being discussed. It then continues with the subject of the sentence - 'the first requirement to being a military test pilot' - and concludes with the essential detail - 'was being male'. This option most clearly and naturally conveys the intended message.
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