In the first paragraph, the author sets up a distinction between two causes of catastrophe. There are powerful mechanisms, and there are minor events (the drop of a pin.)
The second paragraph discusses the traditional study of large systems. They were studied in the same way as small systems. Basically, a large interactive system is just the sum of its smaller parts.
In paragraph three, the author explains the problems with this traditional method, and introduces the newer "theory of self-organized criticality."
The problem with E is that the new approach presented by the author may be non-traditional, but it is not unfashionable. Rather than being "reconsidered," it has become increasingly apparent over the last few decades. The author is not resurrecting an old method. Instead, the author demonstrates in paragraphs 4 and 5 how this new approach is superior, and how it accounts for minor events having major effects. The traditional school of thought failed to do so. This is best expressed by answer choice D.
