If ∑n=1∞an=S\sum_{n=1}^{\infty} a_n = S∑n=1∞an=S, which of the following must be true?
limn→∞an=0\lim_{n \to \infty} a_n = 0limn→∞an=0
limn→∞Sn=0\lim_{n \to \infty} S_n = 0limn→∞Sn=0
∑n=1∞∣an∣\sum_{n=1}^{\infty} |a_n|∑n=1∞∣an∣ converges
∑n=1∞an2\sum_{n=1}^{\infty} a_n^2∑n=1∞an2 converges