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Combinatorics Difficulty 3.0 AMC 10/12 Find the answer United Kingdom

There are $30$ students in a class. They sit in pairs so that each boy is sitting next to a girl and exactly half of the girls are sitting next to a boy. How many boys are there in the class?

(A) $25$ (B) $20$ (C) $15$ (D) $10$ (E) $5$

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