SAT Question a153ad6a: Boundaries answer and explanation

English - Boundaries - Semicolon Between Independent Clauses
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While light is known as one of the fastest-moving substances, it slows down when passing through some types of matter. One such type of matter is a form of cooled, condensed gas called a Bose-Einstein condensate ______ Dutch physicist Lene Hau famously used a BEC to slow a beam of light to a complete halt.
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Difficulty:Medium
Which choice completes the text so that it conforms to the conventions of Standard English?