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Combinatorics Difficulty 2.0 Junior Find the answer United Kingdom

Eight unmarked envelopes contain the numbers: 1, 2, 4, 8, 16, 32, 64, 128. Eve chooses a few envelopes randomly. Alie takes the rest. Both sum up their numbers. Eve's sum is 31 more than Alie's. How many envelopes did Eve take?

(A) $2$ (B) $3$ (C) $4$ (D) $5$ (E) $6$

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