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CEMC Gauss (Grade 8), 1999

Combinatorics Difficulty 1.0 Junior Find the answer Canada

Tom spent part of his morning visiting and playing with friends. The graph shows his travels. He went to his friends' houses and stopped to play if they were at home. The number of houses at which he stopped to play is

(A) $1$ (B) $2$ (C) $3$ (D) $4$ (E) $5$

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