I would disagree because the ice age was nothing but ice.
I believe the answer is: a. to enhance credibility
Personal experience would give the readers with a certain level of assurance that the writers at least know what they are talking about.
For example, let's say that there are two authors of a self defense book. The first author has an experience as a president's bodyguard while the second author is a full time web designer. Most people would most likely see the first author as the more credible one.
<span>The ideas put forward in his work represented a radical departure from the then-dominant economic policy and philosophy of mercantilism, which had held sway in Europe for three centuries.</span>
