If log a, log b, log c are in A.P. then ?

1. a, b, c are in G.P.
2. a², b², c² are in G.P.
3. a, b, c are in A.P.
4. None of these

∵ loga, logb, logc are in A.P. Then,
⇒ logb - loga = logc - logb
⇒ log b/a = log c/b
⇒ b/a = c/b
⇒ b² = ac
∴ a, b, c are in G.P.