In the following dialogue, which discussion technique does daniel most clearly show?

daniel:
did you guys feel the article was biased? kim sato is a newscaster from japan. since newscasters get money and fame when they deliver a big story, i think that it's possible that kim just wants to stir up some controversy.

a. challenging established ideas
b. assess the claims of others
c. conducting research to support conclusions
d. asking clarifying questions