Unused tunnel and give reasons for people to use it is it safe​

According to that blurb, tunnels are “some of the safest places to be during an earthquake.” Jean-Philippe Avouac, geology professor at Caltech, more or less agrees. “Structures which are underground are less vulnerable to shaking than structures at the surface,” he says. “That's just the effect of inertia."

Explanation:

the underlined phrase is an example of : understatment

the sentence that best describes the tone of the passage from the radio broadcast compared to the passage from the book is b. the radio broadcast has a more surprised tone.

consider the text evidence: in the passage from the book, the description is more matter-of-fact. it is simply describing the things resembling little grey snakes, but there is no urgency in the description. on the other hand, in the passage from the radio broadcast, there is definetely urgency (you can tell from the expression used, "good heavens", which clearly indicates surprise.)