Task: Question Answering
Input (English): \begin { gather* } 5, 5k, 5k^2 , 5k^3 , ...\end { gather* } The first term in the sequence above is 5, and each term after the first is \(k\) times the preceding term. If the sum of the first three terms is 15, which of the following could be the value of \(k\) ?
(A)-2 (B)-1 (C)0 (D)2 (E)3
Output (English): A