Jonas Salk<span> </span><span>was an American </span>medical researcher<span> and </span>virologist<span>. He discovered and developed one of the first successful </span>polio vaccines in the 1950's.
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During which dynasty did trade on the Silk Road reach its peak? Question 3 options: Shang Qin Tang Song
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Action taken by a country whose exports are adversely affected by the raising of tariff or other trade-restricting measures by another country. Also called retorsion
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