If A1 = 1, then S4 = () A. 7B. 8C. 15D. 16

∵ 4A1, 2A2, A3 are arithmetic sequences ∵ 4A1 + A32 = & nbsp; 2A2, ∵ 4A1 + A1 · q22 = 2a1q, that is, 4 + q22 = 2 & nbsp; Q ∵ q = 2 ∵ S4 = A1 (1 − Q4) 1 − q = 1 × (1 − 24) 1 − 2 = 15, so select C

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