They change shape due to a number of reasons.
The easiest reason to understand why they change is that they erode.
The coasts around the the world erode due to waves hitting cliffs, the wind batting against the coasts etc. Over a long period of time we can see that they change in shape.
(sorry I don't know why they move)
Answer: B. challenging established ideas.
Explanation: In the given conversation, we can see that Han is asking a question about a published article, he is asking about whether or not the article was biased because the writer could only want to stir up a controversy to get money and fame. By asking that question Han is showing the group discussion technique of challenging established ideas, so the correct answer is option B.
