Which of these infinite series represents a divergent geometric series?
∑n=1∞(0.9)n−1\sum_{n=1}^{\infty} (0.9)^{n-1}∑n=1∞(0.9)n−1
∑n=1∞(1.1)n−1\sum_{n=1}^{\infty} (1.1)^{n-1}∑n=1∞(1.1)n−1
∑n=1∞(−0.5)n−1\sum_{n=1}^{\infty} (-0.5)^{n-1}∑n=1∞(−0.5)n−1
∑n=1∞(1/10)n\sum_{n=1}^{\infty} (1/10)^n∑n=1∞(1/10)n