Seven people - A, B, C, D, E, F and G - are standing in a single line, facing a booth. E is somewhere ahead of F. There is exactly one person standing between C and G. D is immediately behind A. F is behind both B and D. If D and C are fourth and fifth in line respectively, then which of the following must be true?
A F is seventh
B A is first
C F is sixth
D B is first
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