We don’t know that the author agrees with Garber. So we can’t say the author believes the Dutch tulip market is “mistakenly” believed to be an example of a speculative bubble. It’s also not clear that the belief the market is a speculative bubble is “widely” held.

There’s no support for this. The passage doesn’t suggest that Mackay had any thoughts or assessments of the potential earnings from Dutch tulip bulbs. Although Garber describes potential earnings, this doesn’t imply anything about Mackay’s views about those earnings. Also, the author doesn’t necessarily agree with Garber. She merely reports Garber’s views. So we have no reason to think the author would call Mackay wrong or inaccurate about something.

This isn’t supported, because if a decline is driven by the “asset’s fundamentals,” then it’s not necessarily a speculative bubble. Also, Garber argued that the tulip market was not necessarily a speculative bubble; (C) doesn’t capture this view.

This best captures the main point. Garber criticizes Mackay’s view that the Dutch tulip market was a speculative bubble. In P3, the author explains Garber’s reasoning.

(E) is supported by the passage at the end, but it’s not the main point. It’s part of the reasoning supporting Garber’s criticism of Mackay’s view. The main point is Garber’s criticism.