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AB / DE = BC / EF = 1/3
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Options
BC / EF = 4/6 = 2/3 (not possible)
BC / EF = 3/9 = 1/3
BC / EF = 3 /10 (not possible)
BC / EF = 3/12 = 1/4 (not possible)
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Answer
BC / EF = 3/9 = 1/3