About the conversation topics in different cultures, which of the following statements are correct?
选项：

A:For many cultures, the relatively safe conversation topics include: weather, environment, sports, hobbies, etc.;
B:The obstacles to talking about sports, hobbies and other topics with foreigners lie in the lack of understanding of some cultural background knowledge.;
C:Inappropriate conversation topics for some cultures are inappropriate in all cultures.;
D:Religion and politics are the two most inappropriate topics.