It was not until 1911, _______ the first vitamin was identified, _______ people realized the importance of it.
A.when; which | B.when; that | C.that; which | D.that; that |
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It was not until 1911, _______ the first vitamin was identified, _______ people realized the importance of it.
A.when; which | B.when; that | C.that; which | D.that; that |