听力原文：M: Doctor Cole, thank you for agreeing to this interview for the Daily Campus News. Can you tell us about what you and your colleagues discussed at the annual astronomy society meeting last month？
W: Sure. For the first time ever, the scientific community has established the existence of planets outside our own solar system. Of course we knew that certain distant stars existed. But only recently did we learn that several of them are orbited by their own planets.
M: Why did it take so long to locate these planets？
W: You have to understand that they are a billion times dimmer than their parent stars. It would be like trying to see the light of a candle next to a huge explosion. We don't currently have a telescope that can be used to see them.
M: But if the astronomers didn't see the planets through a telescope, how could they find them？
W: By an indirect method. It is hard to describe it with one or two words.
M: There is a powerful new telescope being built in Arizona. Will that help them see these planets？
W: They should be able to see them at least in the form. of small spots of light, and then the scientists would be able to break down and analyze the light. By doing this, they hope to learn about the chemical composition of these planets.
M: I'm looking forward to hearing more when the telescope is in operation. And I'm sure our readers will be interested in it, too.
When was the annual astronomy society meeting held？

A. Last year.
B. Last month.
C. Two days ago.
D. Two months ago.